Rename NavigationObserver and BrowserObserver to NavigationCallback and BrowserCallback.

This is more aligned with Android style guide.

Change-Id: I503748a796e2e5934e92d6ec9c6963907debabbb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1890824
Commit-Queue: John Abd-El-Malek <jam@chromium.org>
Reviewed-by: Clark DuVall <cduvall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#711128}

weblayer/BUILD.gn

@@ -174,8 +174,8 @@ jumbo_static_library("weblayer_lib") {
     sources += [
       "app/jni_onload.cc",
       "app/jni_onload.h",
-      "browser/browser_observer_proxy.cc",
-      "browser/browser_observer_proxy.h",
+      "browser/browser_callback_proxy.cc",
+      "browser/browser_callback_proxy.h",
       "browser/content_view_render_view.cc",
       "browser/content_view_render_view.h",
       "browser/download_delegate_proxy.cc",

weblayer/browser/browser_observer_proxy.cc → weblayer/browser/browser_callback_proxy.cc

@@ -2,12 +2,12 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "weblayer/browser/browser_observer_proxy.h"
+#include "weblayer/browser/browser_callback_proxy.h"
 
 #include "base/android/jni_string.h"
 #include "url/gurl.h"
 #include "weblayer/browser/browser_controller_impl.h"
-#include "weblayer/browser/java/jni/BrowserObserverProxy_jni.h"
+#include "weblayer/browser/java/jni/BrowserCallbackProxy_jni.h"
 
 using base::android::AttachCurrentThread;
 using base::android::ConvertUTF8ToJavaString;
@@ -15,7 +15,7 @@ using base::android::ScopedJavaLocalRef;
 
 namespace weblayer {
 
-BrowserObserverProxy::BrowserObserverProxy(
+BrowserCallbackProxy::BrowserCallbackProxy(
     JNIEnv* env,
     jobject obj,
     BrowserController* browser_controller)
@@ -23,29 +23,29 @@ BrowserObserverProxy::BrowserObserverProxy(
   browser_controller_->AddObserver(this);
 }
 
-BrowserObserverProxy::~BrowserObserverProxy() {
+BrowserCallbackProxy::~BrowserCallbackProxy() {
   browser_controller_->RemoveObserver(this);
 }
 
-void BrowserObserverProxy::DisplayedUrlChanged(const GURL& url) {
+void BrowserCallbackProxy::DisplayedUrlChanged(const GURL& url) {
   JNIEnv* env = AttachCurrentThread();
   ScopedJavaLocalRef<jstring> jstring_url(
       ConvertUTF8ToJavaString(env, url.spec()));
-  Java_BrowserObserverProxy_visibleUrlChanged(env, java_observer_, jstring_url);
+  Java_BrowserCallbackProxy_visibleUrlChanged(env, java_observer_, jstring_url);
 }
 
-static jlong JNI_BrowserObserverProxy_CreateBrowserObserverProxy(
+static jlong JNI_BrowserCallbackProxy_CreateBrowserCallbackProxy(
     JNIEnv* env,
     const base::android::JavaParamRef<jobject>& proxy,
     jlong browser_controller) {
-  return reinterpret_cast<jlong>(new BrowserObserverProxy(
+  return reinterpret_cast<jlong>(new BrowserCallbackProxy(
       env, proxy,
       reinterpret_cast<BrowserControllerImpl*>(browser_controller)));
 }
 
-static void JNI_BrowserObserverProxy_DeleteBrowserObserverProxy(JNIEnv* env,
+static void JNI_BrowserCallbackProxy_DeleteBrowserCallbackProxy(JNIEnv* env,
                                                                 jlong proxy) {
-  delete reinterpret_cast<BrowserObserverProxy*>(proxy);
+  delete reinterpret_cast<BrowserCallbackProxy*>(proxy);
 }
 
 }  // namespace weblayer

weblayer/browser/browser_observer_proxy.h → weblayer/browser/browser_callback_proxy.h

@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#ifndef WEBLAYER_BROWSER_BROWSER_OBSERVER_PROXY_H_
-#define WEBLAYER_BROWSER_BROWSER_OBSERVER_PROXY_H_
+#ifndef WEBLAYER_BROWSER_BROWSER_CALLBACK_PROXY_H_
+#define WEBLAYER_BROWSER_BROWSER_CALLBACK_PROXY_H_
 
 #include <jni.h>
 
@@ -15,14 +15,14 @@ namespace weblayer {
 
 class BrowserController;
 
-// BrowserObserverProxy forwards all BrowserObserver functions to the Java
-// side. There is one BrowserObserverProxy per BrowserController.
-class BrowserObserverProxy : public BrowserObserver {
+// BrowserCallbackProxy forwards all BrowserObserver functions to the Java
+// side. There is one BrowserCallbackProxy per BrowserController.
+class BrowserCallbackProxy : public BrowserObserver {
  public:
-  BrowserObserverProxy(JNIEnv* env,
+  BrowserCallbackProxy(JNIEnv* env,
                        jobject obj,
                        BrowserController* browser_controller);
-  ~BrowserObserverProxy() override;
+  ~BrowserCallbackProxy() override;
 
   // BrowserObserver:
   void DisplayedUrlChanged(const GURL& url) override;
@@ -31,9 +31,9 @@ class BrowserObserverProxy : public BrowserObserver {
   BrowserController* browser_controller_;
   base::android::ScopedJavaGlobalRef<jobject> java_observer_;
 
-  DISALLOW_COPY_AND_ASSIGN(BrowserObserverProxy);
+  DISALLOW_COPY_AND_ASSIGN(BrowserCallbackProxy);
 };
 
 }  // namespace weblayer
 
-#endif  // WEBLAYER_BROWSER_BROWSER_OBSERVER_PROXY_H_
+#endif  // WEBLAYER_BROWSER_BROWSER_CALLBACK_PROXY_H_

weblayer/browser/java/BUILD.gn

@@ -26,7 +26,7 @@ android_library("java") {
     "org/chromium/weblayer_private/BrowserControllerImpl.java",
     "org/chromium/weblayer_private/BrowserFragmentControllerImpl.java",
     "org/chromium/weblayer_private/BrowserFragmentImpl.java",
-    "org/chromium/weblayer_private/BrowserObserverProxy.java",
+    "org/chromium/weblayer_private/BrowserCallbackProxy.java",
     "org/chromium/weblayer_private/ChildProcessServiceImpl.java",
     "org/chromium/weblayer_private/ContentView.java",
     "org/chromium/weblayer_private/ContentViewRenderView.java",
@@ -69,8 +69,8 @@ android_library("java") {
 
 generate_jni("jni") {
   sources = [
+    "org/chromium/weblayer_private/BrowserCallbackProxy.java",
     "org/chromium/weblayer_private/BrowserControllerImpl.java",
-    "org/chromium/weblayer_private/BrowserObserverProxy.java",
     "org/chromium/weblayer_private/ContentViewRenderView.java",
     "org/chromium/weblayer_private/DownloadDelegateProxy.java",
     "org/chromium/weblayer_private/FullscreenDelegateProxy.java",

weblayer/browser/java/org/chromium/weblayer_private/BrowserObserverProxy.java → weblayer/browser/java/org/chromium/weblayer_private/BrowserCallbackProxy.java

@@ -12,24 +12,24 @@ import org.chromium.base.annotations.NativeMethods;
 import org.chromium.weblayer_private.aidl.IBrowserControllerClient;
 
 /**
- * Owns the c++ BrowserObserverProxy class, which is responsible for forwarding all
+ * Owns the C++ BrowserCallbackProxy class, which is responsible for forwarding all
  * BrowserObserver calls to this class, which in turn forwards to the BrowserControllerClient.
- * To avoid unnecessary IPC only one BrowserObserverProxy is created per BrowserController.
+ * To avoid unnecessary IPC only one BrowserCallbackProxy is created per BrowserController.
  */
 @JNINamespace("weblayer")
-public final class BrowserObserverProxy {
-    private long mNativeBrowserObserverProxy;
+public final class BrowserCallbackProxy {
+    private long mNativeBrowserCallbackProxy;
     private IBrowserControllerClient mClient;
 
-    BrowserObserverProxy(long browserController, IBrowserControllerClient client) {
+    BrowserCallbackProxy(long browserController, IBrowserControllerClient client) {
         mClient = client;
-        mNativeBrowserObserverProxy =
-                BrowserObserverProxyJni.get().createBrowserObserverProxy(this, browserController);
+        mNativeBrowserCallbackProxy =
+                BrowserCallbackProxyJni.get().createBrowserCallbackProxy(this, browserController);
     }
 
     public void destroy() {
-        BrowserObserverProxyJni.get().deleteBrowserObserverProxy(mNativeBrowserObserverProxy);
-        mNativeBrowserObserverProxy = 0;
+        BrowserCallbackProxyJni.get().deleteBrowserCallbackProxy(mNativeBrowserCallbackProxy);
+        mNativeBrowserCallbackProxy = 0;
     }
 
     @CalledByNative
@@ -39,7 +39,7 @@ public final class BrowserObserverProxy {
 
     @NativeMethods
     interface Natives {
-        long createBrowserObserverProxy(BrowserObserverProxy proxy, long browserController);
-        void deleteBrowserObserverProxy(long proxy);
+        long createBrowserCallbackProxy(BrowserCallbackProxy proxy, long browserController);
+        void deleteBrowserCallbackProxy(long proxy);
     }
 }

weblayer/browser/java/org/chromium/weblayer_private/BrowserControllerImpl.java

@@ -48,7 +48,7 @@ public final class BrowserControllerImpl extends IBrowserController.Stub
     private TopControlsContainerView mTopControlsContainerView;
     private ProfileImpl mProfile;
     private WebContents mWebContents;
-    private BrowserObserverProxy mBrowserObserverProxy;
+    private BrowserCallbackProxy mBrowserCallbackProxy;
     private NavigationControllerImpl mNavigationController;
     private DownloadDelegateProxy mDownloadDelegateProxy;
     private FullscreenDelegateProxy mFullscreenDelegateProxy;
@@ -163,7 +163,7 @@ public final class BrowserControllerImpl extends IBrowserController.Stub
 
     @Override
     public void setClient(IBrowserControllerClient client) {
-        mBrowserObserverProxy = new BrowserObserverProxy(mNativeBrowserController, client);
+        mBrowserCallbackProxy = new BrowserCallbackProxy(mNativeBrowserController, client);
     }
 
     @Override
@@ -217,9 +217,9 @@ public final class BrowserControllerImpl extends IBrowserController.Stub
                 mNativeBrowserController, BrowserControllerImpl.this, 0);
         mTopControlsContainerView.destroy();
         mContentViewRenderView.destroy();
-        if (mBrowserObserverProxy != null) {
-            mBrowserObserverProxy.destroy();
-            mBrowserObserverProxy = null;
+        if (mBrowserCallbackProxy != null) {
+            mBrowserCallbackProxy.destroy();
+            mBrowserCallbackProxy = null;
         }
         if (mDownloadDelegateProxy != null) {
             mDownloadDelegateProxy.destroy();

weblayer/browser/java/org/chromium/weblayer_private/aidl/IBrowserControllerClient.aidl

@@ -6,7 +6,7 @@ package org.chromium.weblayer_private.aidl;
 
 /**
  * Interface used by BrowserController to inform the client of changes. This largely duplicates the
- *  BrowserObserver interface, but is a singleton to avoid unnecessary IPC.
+ * BrowserCallback interface, but is a singleton to avoid unnecessary IPC.
  */
 interface IBrowserControllerClient {
   void visibleUrlChanged(in String url) = 0;

weblayer/browser/java/org/chromium/weblayer_private/aidl/INavigationControllerClient.aidl

@@ -6,7 +6,7 @@ package org.chromium.weblayer_private.aidl;
 
 /**
  * Interface used by NavigationController to inform the client of changes. This largely duplicates
- * the NavigationObserver interface, but is a singleton to avoid unnecessary IPC.
+ * the NavigationCallback interface, but is a singleton to avoid unnecessary IPC.
  */
 interface INavigationControllerClient {
   IClientNavigation createClientNavigation(in INavigation impl) = 0;

weblayer/public/java/BUILD.gn

@@ -21,10 +21,10 @@ android_resources("client_resources") {
 
 android_library("java") {
   java_files = [
+    "org/chromium/weblayer/BrowserCallback.java",
     "org/chromium/weblayer/BrowserController.java",
     "org/chromium/weblayer/BrowserFragmentController.java",
     "org/chromium/weblayer/BrowserFragment.java",
-    "org/chromium/weblayer/BrowserObserver.java",
     "org/chromium/weblayer/BrowsingDataType.java",
     "org/chromium/weblayer/Callback.java",
     "org/chromium/weblayer/ChildProcessService.java",
@@ -32,16 +32,16 @@ android_library("java") {
     "org/chromium/weblayer/FullscreenDelegate.java",
     "org/chromium/weblayer/ListenableFuture.java",
     "org/chromium/weblayer/ListenableResult.java",
-    "org/chromium/weblayer/WebLayerFileProvider.java",
+    "org/chromium/weblayer/NavigationCallback.java",
     "org/chromium/weblayer/NavigationController.java",
     "org/chromium/weblayer/Navigation.java",
-    "org/chromium/weblayer/NavigationObserver.java",
     "org/chromium/weblayer/ObserverList.java",
     "org/chromium/weblayer/Profile.java",
     "org/chromium/weblayer/ProfileManager.java",
     "org/chromium/weblayer/ThreadCheck.java",
     "org/chromium/weblayer/UnsupportedVersionException.java",
     "org/chromium/weblayer/WebLayer.java",
+    "org/chromium/weblayer/WebLayerFileProvider.java",
   ]
 
   deps = [

weblayer/public/java/org/chromium/weblayer/BrowserObserver.java → weblayer/public/java/org/chromium/weblayer/BrowserCallback.java

@@ -11,7 +11,7 @@ import androidx.annotation.NonNull;
 /**
  * Informed of interesting events that happen during the lifetime of a BrowserController.
  */
-public abstract class BrowserObserver {
+public abstract class BrowserCallback {
     /**
      * The Uri that should be displayed in the url-bar has updated.
      *

weblayer/public/java/org/chromium/weblayer/BrowserController.java

@@ -24,7 +24,7 @@ import org.chromium.weblayer_private.aidl.ObjectWrapper;
 
 /**
  * Represents a web-browser. More specifically, owns a NavigationController, and allows configuring
- * state of the browser, such as delegates and observers.
+ * state of the browser, such as delegates and callbacks.
  */
 public final class BrowserController {
     /** The top level key of the JSON object returned by executeScript(). */
@@ -33,7 +33,7 @@ public final class BrowserController {
     private final IBrowserController mImpl;
     private FullscreenDelegateClientImpl mFullscreenDelegateClient;
     private final NavigationController mNavigationController;
-    private final ObserverList<BrowserObserver> mObservers;
+    private final ObserverList<BrowserCallback> mCallbacks;
     private DownloadDelegateClientImpl mDownloadDelegateClient;
 
     BrowserController(IBrowserController impl) {
@@ -44,7 +44,7 @@ public final class BrowserController {
             throw new APICallException(e);
         }
 
-        mObservers = new ObserverList<BrowserObserver>();
+        mCallbacks = new ObserverList<BrowserCallback>();
         mNavigationController = NavigationController.create(mImpl);
     }
 
@@ -128,14 +128,14 @@ public final class BrowserController {
         return mNavigationController;
     }
 
-    public void addObserver(@Nullable BrowserObserver observer) {
+    public void registerBrowserCallback(@Nullable BrowserCallback callback) {
         ThreadCheck.ensureOnUiThread();
-        mObservers.addObserver(observer);
+        mCallbacks.addObserver(callback);
     }
 
-    public void removeObserver(@Nullable BrowserObserver observer) {
+    public void unregisterBrowserCallback(@Nullable BrowserCallback callback) {
         ThreadCheck.ensureOnUiThread();
-        mObservers.removeObserver(observer);
+        mCallbacks.removeObserver(callback);
     }
 
     IBrowserController getIBrowserController() {
@@ -146,8 +146,8 @@ public final class BrowserController {
         @Override
         public void visibleUrlChanged(String url) {
             Uri uri = Uri.parse(url);
-            for (BrowserObserver observer : mObservers) {
-                observer.visibleUrlChanged(uri);
+            for (BrowserCallback callback : mCallbacks) {
+                callback.visibleUrlChanged(uri);
             }
         }
     }

weblayer/public/java/org/chromium/weblayer/NavigationObserver.java → weblayer/public/java/org/chromium/weblayer/NavigationCallback.java

@@ -17,7 +17,7 @@ import androidx.annotation.NonNull;
  * 4) navigationCompleted() or navigationFailed()
  * 5) onFirstContentfulPaint
  */
-public abstract class NavigationObserver {
+public abstract class NavigationCallback {
     /**
      * Called when a navigation started in the BrowserController. |navigation| is unique to a
      * specific navigation. The same |navigation| will be  provided on subsequent calls to

weblayer/public/java/org/chromium/weblayer/NavigationController.java

@@ -21,7 +21,7 @@ import org.chromium.weblayer_private.aidl.INavigationControllerClient;
  */
 public final class NavigationController {
     private INavigationController mNavigationController;
-    private final ObserverList<NavigationObserver> mObservers;
+    private final ObserverList<NavigationCallback> mCallbacks;
 
     static NavigationController create(IBrowserController browserController) {
         NavigationController navigationController = new NavigationController();
@@ -36,7 +36,7 @@ public final class NavigationController {
     }
 
     private NavigationController() {
-        mObservers = new ObserverList<NavigationObserver>();
+        mCallbacks = new ObserverList<NavigationCallback>();
     }
 
     public void navigate(@NonNull Uri uri) {
@@ -130,14 +130,14 @@ public final class NavigationController {
         }
     }
 
-    public void addObserver(@NonNull NavigationObserver observer) {
+    public void registerNavigationCallback(@NonNull NavigationCallback callback) {
         ThreadCheck.ensureOnUiThread();
-        mObservers.addObserver(observer);
+        mCallbacks.addObserver(callback);
     }
 
-    public void removeObserver(@NonNull NavigationObserver observer) {
+    public void unregisterNavigationCallback(@NonNull NavigationCallback callback) {
         ThreadCheck.ensureOnUiThread();
-        mObservers.removeObserver(observer);
+        mCallbacks.removeObserver(callback);
     }
 
     private final class NavigationControllerClientImpl extends INavigationControllerClient.Stub {
@@ -148,57 +148,57 @@ public final class NavigationController {
 
         @Override
         public void navigationStarted(IClientNavigation navigation) {
-            for (NavigationObserver observer : mObservers) {
-                observer.navigationStarted((Navigation) navigation);
+            for (NavigationCallback callback : mCallbacks) {
+                callback.navigationStarted((Navigation) navigation);
             }
         }
 
         @Override
         public void navigationRedirected(IClientNavigation navigation) {
-            for (NavigationObserver observer : mObservers) {
-                observer.navigationRedirected((Navigation) navigation);
+            for (NavigationCallback callback : mCallbacks) {
+                callback.navigationRedirected((Navigation) navigation);
             }
         }
 
         @Override
         public void readyToCommitNavigation(IClientNavigation navigation) {
-            for (NavigationObserver observer : mObservers) {
-                observer.readyToCommitNavigation((Navigation) navigation);
+            for (NavigationCallback callback : mCallbacks) {
+                callback.readyToCommitNavigation((Navigation) navigation);
             }
         }
 
         @Override
         public void navigationCompleted(IClientNavigation navigation) {
-            for (NavigationObserver observer : mObservers) {
-                observer.navigationCompleted((Navigation) navigation);
+            for (NavigationCallback callback : mCallbacks) {
+                callback.navigationCompleted((Navigation) navigation);
             }
         }
 
         @Override
         public void navigationFailed(IClientNavigation navigation) {
-            for (NavigationObserver observer : mObservers) {
-                observer.navigationFailed((Navigation) navigation);
+            for (NavigationCallback callback : mCallbacks) {
+                callback.navigationFailed((Navigation) navigation);
             }
         }
 
         @Override
         public void loadStateChanged(boolean isLoading, boolean toDifferentDocument) {
-            for (NavigationObserver observer : mObservers) {
-                observer.loadStateChanged(isLoading, toDifferentDocument);
+            for (NavigationCallback callback : mCallbacks) {
+                callback.loadStateChanged(isLoading, toDifferentDocument);
             }
         }
 
         @Override
         public void loadProgressChanged(double progress) {
-            for (NavigationObserver observer : mObservers) {
-                observer.loadProgressChanged(progress);
+            for (NavigationCallback callback : mCallbacks) {
+                callback.loadProgressChanged(progress);
             }
         }
 
         @Override
         public void onFirstContentfulPaint() {
-            for (NavigationObserver observer : mObservers) {
-                observer.onFirstContentfulPaint();
+            for (NavigationCallback callback : mCallbacks) {
+                callback.onFirstContentfulPaint();
             }
         }
     }

weblayer/shell/android/BUILD.gn

@@ -211,7 +211,7 @@ instrumentation_test_apk("weblayer_instrumentation_test_apk") {
     "//third_party/android_support_test_runner:runner_java",
   ]
   java_files = [
-    "javatests/src/org/chromium/weblayer/test/BrowserObserverTest.java",
+    "javatests/src/org/chromium/weblayer/test/BrowserCallbackTest.java",
     "javatests/src/org/chromium/weblayer/test/DataClearingTest.java",
     "javatests/src/org/chromium/weblayer/test/DownloadDelegateTest.java",
     "javatests/src/org/chromium/weblayer/test/EventUtils.java",

weblayer/shell/android/browsertests_apk/src/org/chromium/weblayer_browsertests_apk/WebLayerBrowserTestsActivity.java

@@ -18,9 +18,9 @@ import org.chromium.base.test.util.UrlUtils;
 import org.chromium.content_public.browser.BrowserStartupController;
 import org.chromium.native_test.NativeBrowserTest;
 import org.chromium.native_test.NativeBrowserTestActivity;
+import org.chromium.weblayer.BrowserCallback;
 import org.chromium.weblayer.BrowserController;
 import org.chromium.weblayer.BrowserFragmentController;
-import org.chromium.weblayer.BrowserObserver;
 import org.chromium.weblayer.Profile;
 import org.chromium.weblayer.WebLayer;
 
@@ -88,7 +88,7 @@ public class WebLayerBrowserTestsActivity extends NativeBrowserTestActivity {
         mBrowserFragmentController.setTopView(topContentsContainer);
 
         mBrowserController = mBrowserFragmentController.getBrowserController();
-        mBrowserController.addObserver(new BrowserObserver() {
+        mBrowserController.registerBrowserCallback(new BrowserCallback() {
             @Override
             public void visibleUrlChanged(Uri uri) {
                 mUrlView.setText(uri.toString());

weblayer/shell/android/javatests/src/org/chromium/weblayer/test/BrowserObserverTest.java → weblayer/shell/android/javatests/src/org/chromium/weblayer/test/BrowserCallbackTest.java

@@ -15,7 +15,7 @@ import org.chromium.base.test.BaseJUnit4ClassRunner;
 import org.chromium.content_public.browser.test.util.Criteria;
 import org.chromium.content_public.browser.test.util.CriteriaHelper;
 import org.chromium.content_public.browser.test.util.TestThreadUtils;
-import org.chromium.weblayer.BrowserObserver;
+import org.chromium.weblayer.BrowserCallback;
 import org.chromium.weblayer.shell.InstrumentationActivity;
 
 import java.util.ArrayList;
@@ -23,16 +23,16 @@ import java.util.Collections;
 import java.util.List;
 
 /**
- * Tests that BrowserObserver methods are invoked as expected.
+ * Tests that BrowserCallback methods are invoked as expected.
  */
 @RunWith(BaseJUnit4ClassRunner.class)
-public class BrowserObserverTest {
+public class BrowserCallbackTest {
     @Rule
     public InstrumentationActivityTestRule mActivityTestRule =
             new InstrumentationActivityTestRule();
 
-    private static class Observer extends BrowserObserver {
-        public static class BrowserObserverValueRecorder {
+    private static class Callback extends BrowserCallback {
+        public static class BrowserCallbackValueRecorder {
             private List<String> mObservedValues =
                     Collections.synchronizedList(new ArrayList<String>());
 
@@ -57,8 +57,8 @@ public class BrowserObserverTest {
             }
         }
 
-        public BrowserObserverValueRecorder visibleUrlChangedCallback =
-                new BrowserObserverValueRecorder();
+        public BrowserCallbackValueRecorder visibleUrlChangedCallback =
+                new BrowserCallbackValueRecorder();
 
         @Override
         public void visibleUrlChanged(Uri url) {
@@ -72,14 +72,14 @@ public class BrowserObserverTest {
         String startupUrl = "about:blank";
         InstrumentationActivity activity = mActivityTestRule.launchShellWithUrl(startupUrl);
 
-        Observer observer = new Observer();
+        Callback calllback = new Callback();
         TestThreadUtils.runOnUiThreadBlocking(
-                () -> { activity.getBrowserController().addObserver(observer); });
+                () -> { activity.getBrowserController().registerBrowserCallback(calllback); });
 
         String url = "data:text,foo";
         mActivityTestRule.navigateAndWait(url);
 
         /* Verify that the visible URL changes to the target. */
-        observer.visibleUrlChangedCallback.waitUntilValueObserved(url);
+        calllback.visibleUrlChangedCallback.waitUntilValueObserved(url);
     }
 }

weblayer/shell/android/javatests/src/org/chromium/weblayer/test/InstrumentationActivityTestRule.java

@@ -22,7 +22,7 @@ import org.chromium.content_public.browser.test.util.CriteriaHelper;
 import org.chromium.content_public.browser.test.util.TestThreadUtils;
 import org.chromium.weblayer.BrowserController;
 import org.chromium.weblayer.Navigation;
-import org.chromium.weblayer.NavigationObserver;
+import org.chromium.weblayer.NavigationCallback;
 import org.chromium.weblayer.shell.InstrumentationActivity;
 
 import java.lang.reflect.Field;
@@ -41,7 +41,7 @@ public class InstrumentationActivityTestRule extends ActivityTestRule<Instrument
         private boolean mDoneLoading;
         private CallbackHelper mCallbackHelper = new CallbackHelper();
 
-        private NavigationObserver mNavigationObserver = new NavigationObserver() {
+        private NavigationCallback mNavigationCallback = new NavigationCallback() {
             @Override
             public void navigationCompleted(Navigation navigation) {
                 if (navigation.getUri().toString().equals(mUrl)) {
@@ -64,7 +64,8 @@ public class InstrumentationActivityTestRule extends ActivityTestRule<Instrument
 
         public void navigateAndWait() {
             TestThreadUtils.runOnUiThreadBlocking(() -> {
-                mController.getNavigationController().addObserver(mNavigationObserver);
+                mController.getNavigationController().registerNavigationCallback(
+                        mNavigationCallback);
                 mController.getNavigationController().navigate(Uri.parse(mUrl));
             });
             try {
@@ -73,7 +74,8 @@ public class InstrumentationActivityTestRule extends ActivityTestRule<Instrument
                 throw new RuntimeException(e);
             }
             TestThreadUtils.runOnUiThreadBlocking(() -> {
-                mController.getNavigationController().removeObserver(mNavigationObserver);
+                mController.getNavigationController().unregisterNavigationCallback(
+                        mNavigationCallback);
             });
         }
 

weblayer/shell/android/javatests/src/org/chromium/weblayer/test/NavigationTest.java

@@ -23,8 +23,8 @@ import org.chromium.base.test.util.CallbackHelper;
 import org.chromium.content_public.browser.test.util.Criteria;
 import org.chromium.content_public.browser.test.util.CriteriaHelper;
 import org.chromium.weblayer.Navigation;
+import org.chromium.weblayer.NavigationCallback;
 import org.chromium.weblayer.NavigationController;
-import org.chromium.weblayer.NavigationObserver;
 import org.chromium.weblayer.shell.InstrumentationActivity;
 
 import java.util.ArrayList;
@@ -46,7 +46,7 @@ public class NavigationTest {
     private static final String URL2 = "data:text,bar";
     private static final String URL3 = "data:text,baz";
 
-    private static class Observer extends NavigationObserver {
+    private static class Callback extends NavigationCallback {
         public static class NavigationCallbackHelper extends CallbackHelper {
             private Uri mUri;
             private boolean mIsSameDocument;
@@ -75,7 +75,7 @@ public class NavigationTest {
             }
         }
 
-        public static class NavigationObserverValueRecorder {
+        public static class NavigationCallbackValueRecorder {
             private List<String> mObservedValues =
                     Collections.synchronizedList(new ArrayList<String>());
 
@@ -103,10 +103,10 @@ public class NavigationTest {
         public NavigationCallbackHelper onStartedCallback = new NavigationCallbackHelper();
         public NavigationCallbackHelper onReadyToCommitCallback = new NavigationCallbackHelper();
         public NavigationCallbackHelper onCompletedCallback = new NavigationCallbackHelper();
-        public NavigationObserverValueRecorder loadStateChangedCallback =
-                new NavigationObserverValueRecorder();
-        public NavigationObserverValueRecorder loadProgressChangedCallback =
-                new NavigationObserverValueRecorder();
+        public NavigationCallbackValueRecorder loadStateChangedCallback =
+                new NavigationCallbackValueRecorder();
+        public NavigationCallbackValueRecorder loadProgressChangedCallback =
+                new NavigationCallbackValueRecorder();
         public CallbackHelper onFirstContentfulPaintCallback = new CallbackHelper();
 
         @Override
@@ -142,50 +142,50 @@ public class NavigationTest {
         }
     }
 
-    private final Observer mObserver = new Observer();
+    private final Callback mCallback = new Callback();
 
     @Test
     @SmallTest
     public void testNavigationEvents() throws Exception {
         InstrumentationActivity activity = mActivityTestRule.launchShellWithUrl(URL1);
 
-        setNavigationObserver(activity);
-        int curStartedCount = mObserver.onStartedCallback.getCallCount();
-        int curCommittedCount = mObserver.onReadyToCommitCallback.getCallCount();
-        int curCompletedCount = mObserver.onCompletedCallback.getCallCount();
+        setNavigationCallback(activity);
+        int curStartedCount = mCallback.onStartedCallback.getCallCount();
+        int curCommittedCount = mCallback.onReadyToCommitCallback.getCallCount();
+        int curCompletedCount = mCallback.onCompletedCallback.getCallCount();
         int curOnFirstContentfulPaintCount =
-                mObserver.onFirstContentfulPaintCallback.getCallCount();
+                mCallback.onFirstContentfulPaintCallback.getCallCount();
 
         mActivityTestRule.navigateAndWait(URL2);
 
-        mObserver.onStartedCallback.assertCalledWith(curStartedCount, URL2);
-        mObserver.onReadyToCommitCallback.assertCalledWith(curCommittedCount, URL2);
-        mObserver.onCompletedCallback.assertCalledWith(curCompletedCount, URL2);
-        mObserver.onFirstContentfulPaintCallback.waitForCallback(curOnFirstContentfulPaintCount);
+        mCallback.onStartedCallback.assertCalledWith(curStartedCount, URL2);
+        mCallback.onReadyToCommitCallback.assertCalledWith(curCommittedCount, URL2);
+        mCallback.onCompletedCallback.assertCalledWith(curCompletedCount, URL2);
+        mCallback.onFirstContentfulPaintCallback.waitForCallback(curOnFirstContentfulPaintCount);
     }
 
     @Test
     @SmallTest
     public void testLoadStateUpdates() throws Exception {
         InstrumentationActivity activity = mActivityTestRule.launchShellWithUrl(null);
-        setNavigationObserver(activity);
+        setNavigationCallback(activity);
         mActivityTestRule.navigateAndWait(URL1);
 
-        /* Wait until the NavigationObserver is notified of load completion. */
-        mObserver.loadStateChangedCallback.waitUntilValueObserved("false false");
-        mObserver.loadProgressChangedCallback.waitUntilValueObserved("load complete");
+        /* Wait until the NavigationCallback is notified of load completion. */
+        mCallback.loadStateChangedCallback.waitUntilValueObserved("false false");
+        mCallback.loadProgressChangedCallback.waitUntilValueObserved("load complete");
 
-        /* Verify that the NavigationObserver was notified of load progress /before/ load
+        /* Verify that the NavigationCallback was notified of load progress /before/ load
          * completion.
          */
         int finishStateIndex =
-                mObserver.loadStateChangedCallback.getObservedValues().indexOf("false false");
+                mCallback.loadStateChangedCallback.getObservedValues().indexOf("false false");
         int finishProgressIndex =
-                mObserver.loadProgressChangedCallback.getObservedValues().indexOf("load complete");
+                mCallback.loadProgressChangedCallback.getObservedValues().indexOf("load complete");
         int startStateIndex =
-                mObserver.loadStateChangedCallback.getObservedValues().lastIndexOf("true true");
+                mCallback.loadStateChangedCallback.getObservedValues().lastIndexOf("true true");
         int startProgressIndex =
-                mObserver.loadProgressChangedCallback.getObservedValues().lastIndexOf(
+                mCallback.loadProgressChangedCallback.getObservedValues().lastIndexOf(
                         "load started");
 
         assertNotEquals(startStateIndex, -1);
@@ -201,7 +201,7 @@ public class NavigationTest {
     @SmallTest
     public void testGoBackAndForward() throws Exception {
         InstrumentationActivity activity = mActivityTestRule.launchShellWithUrl(URL1);
-        setNavigationObserver(activity);
+        setNavigationCallback(activity);
 
         mActivityTestRule.navigateAndWait(URL2);
         mActivityTestRule.navigateAndWait(URL3);
@@ -239,26 +239,27 @@ public class NavigationTest {
     @SmallTest
     public void testSameDocument() throws Exception {
         InstrumentationActivity activity = mActivityTestRule.launchShellWithUrl(URL1);
-        setNavigationObserver(activity);
+        setNavigationCallback(activity);
 
-        int curCompletedCount = mObserver.onCompletedCallback.getCallCount();
+        int curCompletedCount = mCallback.onCompletedCallback.getCallCount();
 
         mActivityTestRule.executeScriptSync("history.pushState(null, '', '#bar');");
 
-        mObserver.onCompletedCallback.assertCalledWith(
+        mCallback.onCompletedCallback.assertCalledWith(
                 curCompletedCount, "data:text,foo#bar", true);
     }
 
-    private void setNavigationObserver(InstrumentationActivity activity) {
-        runOnUiThreadBlocking(() ->
-            activity.getBrowserController().getNavigationController().addObserver(mObserver)
-        );
+    private void setNavigationCallback(InstrumentationActivity activity) {
+        runOnUiThreadBlocking(()
+                                      -> activity.getBrowserController()
+                                                 .getNavigationController()
+                                                 .registerNavigationCallback(mCallback));
     }
 
     private void navigateAndWaitForCompletion(String expectedUrl, Runnable navigateRunnable)
             throws Exception {
-        int currentCallCount = mObserver.onCompletedCallback.getCallCount();
+        int currentCallCount = mCallback.onCompletedCallback.getCallCount();
         runOnUiThreadBlocking(navigateRunnable);
-        mObserver.onCompletedCallback.assertCalledWith(currentCallCount, expectedUrl);
+        mCallback.onCompletedCallback.assertCalledWith(currentCallCount, expectedUrl);
     }
 }

weblayer/shell/android/shell_apk/src/org/chromium/weblayer/shell/InstrumentationActivity.java

@@ -21,9 +21,9 @@ import android.widget.EditText;
 import android.widget.LinearLayout;
 import android.widget.RelativeLayout;
 
+import org.chromium.weblayer.BrowserCallback;
 import org.chromium.weblayer.BrowserController;
 import org.chromium.weblayer.BrowserFragmentController;
-import org.chromium.weblayer.BrowserObserver;
 import org.chromium.weblayer.Profile;
 import org.chromium.weblayer.UnsupportedVersionException;
 import org.chromium.weblayer.WebLayer;
@@ -125,7 +125,7 @@ public class InstrumentationActivity extends FragmentActivity {
         mBrowserFragmentController.setTopView(mTopContentsContainer);
 
         mBrowserController = mBrowserFragmentController.getBrowserController();
-        mBrowserController.addObserver(new BrowserObserver() {
+        mBrowserController.registerBrowserCallback(new BrowserCallback() {
             @Override
             public void visibleUrlChanged(Uri uri) {
                 mUrlView.setText(uri.toString());

weblayer/shell/android/shell_apk/src/org/chromium/weblayer/shell/WebLayerShellActivity.java

@@ -27,13 +27,13 @@ import android.widget.RelativeLayout;
 import android.widget.TextView;
 import android.widget.TextView.OnEditorActionListener;
 
+import org.chromium.weblayer.BrowserCallback;
 import org.chromium.weblayer.BrowserController;
 import org.chromium.weblayer.BrowserFragmentController;
-import org.chromium.weblayer.BrowserObserver;
 import org.chromium.weblayer.DownloadDelegate;
 import org.chromium.weblayer.FullscreenDelegate;
+import org.chromium.weblayer.NavigationCallback;
 import org.chromium.weblayer.NavigationController;
-import org.chromium.weblayer.NavigationObserver;
 import org.chromium.weblayer.Profile;
 import org.chromium.weblayer.UnsupportedVersionException;
 import org.chromium.weblayer.WebLayer;
@@ -172,24 +172,25 @@ public class WebLayerShellActivity extends FragmentActivity {
             startupUrl = "http://google.com";
         }
         loadUrl(startupUrl);
-        mBrowserController.addObserver(new BrowserObserver() {
+        mBrowserController.registerBrowserCallback(new BrowserCallback() {
             @Override
             public void visibleUrlChanged(Uri uri) {
                 mUrlView.setText(uri.toString());
             }
         });
-        mBrowserController.getNavigationController().addObserver(new NavigationObserver() {
-            @Override
-            public void loadStateChanged(boolean isLoading, boolean toDifferentDocument) {
-                mLoadProgressBar.setVisibility(
-                        isLoading && toDifferentDocument ? View.VISIBLE : View.INVISIBLE);
-            }
+        mBrowserController.getNavigationController().registerNavigationCallback(
+                new NavigationCallback() {
+                    @Override
+                    public void loadStateChanged(boolean isLoading, boolean toDifferentDocument) {
+                        mLoadProgressBar.setVisibility(
+                                isLoading && toDifferentDocument ? View.VISIBLE : View.INVISIBLE);
+                    }
 
-            @Override
-            public void loadProgressChanged(double progress) {
-                mLoadProgressBar.setProgress((int) Math.round(100 * progress));
-            }
-        });
+                    @Override
+                    public void loadProgressChanged(double progress) {
+                        mLoadProgressBar.setProgress((int) Math.round(100 * progress));
+                    }
+                });
         mBrowserController.setDownloadDelegate(new DownloadDelegate() {
             @Override
             public void downloadRequested(String url, String userAgent, String contentDisposition,