Chromecast: call ClosePage(), wait 50ms before deleting WebContents.

Without this, Chromecast apps will not have time to handle
window.unload events when user switches to a new app.

R=lcwu@chromium.org,byungchul@chromium.org
BUG=400876

Review URL: https://codereview.chromium.org/601293002

Cr-Commit-Position: refs/heads/master@{#296811}

chromecast/shell/android/apk/src/org/chromium/chromecast/shell/CastShellActivity.java

@@ -120,7 +120,7 @@ public class CastShellActivity extends Activity {
         unregisterBroadcastReceiver();
 
         if (mNativeCastWindow != 0) {
-            mCastWindowManager.stopCastWindow(mNativeCastWindow);
+            mCastWindowManager.stopCastWindow(mNativeCastWindow, false /* gracefully */);
             mNativeCastWindow = 0;
         }
     }
@@ -176,7 +176,7 @@ public class CastShellActivity extends Activity {
 
     protected void finishGracefully() {
         if (mNativeCastWindow != 0) {
-            mCastWindowManager.stopCastWindow(mNativeCastWindow);
+            mCastWindowManager.stopCastWindow(mNativeCastWindow, true /* gracefully */);
             mNativeCastWindow = 0;
         }
     }

chromecast/shell/android/apk/src/org/chromium/chromecast/shell/CastWindowManager.java

@@ -98,10 +98,11 @@ public class CastWindowManager extends FrameLayout {
      * Stops a native cast shell instance created by {@link #launchCastWindow(String)}.
      * @param nativeCastWindow Pointer of native cast shell instance returned
      *        by {@link #launchCastWindow(String)}.
+     * @param gracefully Whether or not to call RVH::ClosePage to deliver unload event.
      * @see #launchCastWindow(String)
      */
-    public void stopCastWindow(long nativeCastWindow) {
-        nativeStopCastWindow(nativeCastWindow);
+    public void stopCastWindow(long nativeCastWindow, boolean gracefully) {
+        nativeStopCastWindow(nativeCastWindow, gracefully);
     }
 
     @SuppressWarnings("unused")
@@ -150,6 +151,7 @@ public class CastWindowManager extends FrameLayout {
 
     private static native void nativeInit(Object shellManagerInstance);
     private static native long nativeLaunchCastWindow(String url);
-    private static native void nativeStopCastWindow(long pointerOfNativeCastWindow);
+    private static native void nativeStopCastWindow(long pointerOfNativeCastWindow,
+            boolean gracefully);
     public static native void nativeEnableDevTools(boolean enable);
 }

chromecast/shell/browser/android/cast_window_android.cc

@@ -4,7 +4,7 @@
 
 #include "chromecast/shell/browser/android/cast_window_android.h"
 
-#include "base/message_loop/message_loop.h"
+#include "base/message_loop/message_loop_proxy.h"
 #include "base/path_service.h"
 #include "chromecast/shell/browser/android/cast_window_manager.h"
 #include "content/public/browser/devtools_agent_host.h"
@@ -17,13 +17,22 @@
 namespace chromecast {
 namespace shell {
 
+namespace {
+
+// The time (in milliseconds) we wait for after a page is closed (i.e.
+// after an app is stopped) before we delete the corresponding WebContents.
+const int kWebContentsDestructionDelayInMs = 50;
+
+}  // namespace
+
 // static
 bool CastWindowAndroid::RegisterJni(JNIEnv* env) {
   return RegisterNativesImpl(env);
 }
 
 CastWindowAndroid::CastWindowAndroid(content::WebContents* web_contents)
-    : content::WebContentsObserver(web_contents) {
+    : content::WebContentsObserver(web_contents),
+      weak_factory_(this) {
 }
 
 CastWindowAndroid::~CastWindowAndroid() {
@@ -71,6 +80,13 @@ CastWindowAndroid* CastWindowAndroid::CreateCastWindowAndroid(
 }
 
 void CastWindowAndroid::Close() {
+  // Close page first, which fires the window.unload event. The WebContents
+  // itself will be destroyed after browser-process has received renderer
+  // notification that the page is closed.
+  web_contents_->GetRenderViewHost()->ClosePage();
+}
+
+void CastWindowAndroid::Destroy() {
   // Note: if multiple windows becomes supported, this may close other devtools
   // sessions.
   content::DevToolsAgentHost::DetachAllClients();
@@ -101,7 +117,29 @@ void CastWindowAndroid::AddNewContents(content::WebContents* source,
 
 void CastWindowAndroid::CloseContents(content::WebContents* source) {
   DCHECK_EQ(source, web_contents_.get());
-  Close();
+
+  // We need to delay the deletion of web_contents_ (currently for 50ms) to
+  // give (and guarantee) the renderer enough time to finish 'onunload'
+  // handler (but we don't want to wait any longer than that to delay the
+  // starting of next app).
+
+  if (base::CommandLine::ForCurrentProcess()->HasSwitch(switches::kTestType)) {
+    // When shutting down in a test context, the last remaining WebContents
+    // is torn down at browser-thread shutdown time. Call Destroy directly to
+    // avoid losing the last posted task to delete this object.
+    // TODO(gunsch): This could probably be avoided by using a
+    // CompletionCallback in StopCurrentApp to wait until the app is completely
+    // stopped. This might require a separate message loop and might only be
+    // appropriate for test contexts or during shutdown, since it triggers a
+    // wait on the main thread.
+    Destroy();
+    return;
+  }
+
+  base::MessageLoopProxy::current()->PostDelayedTask(
+      FROM_HERE,
+      base::Bind(&CastWindowAndroid::Destroy, weak_factory_.GetWeakPtr()),
+      base::TimeDelta::FromMilliseconds(kWebContentsDestructionDelayInMs));
 }
 
 bool CastWindowAndroid::CanOverscrollContent() const {
@@ -128,7 +166,7 @@ void CastWindowAndroid::DeactivateContents(content::WebContents* contents) {
 
 void CastWindowAndroid::RenderProcessGone(base::TerminationStatus status) {
   LOG(ERROR) << "Render process gone: status=" << status;
-  Close();
+  Destroy();
 }
 
 }  // namespace shell

chromecast/shell/browser/android/cast_window_android.h

@@ -15,6 +15,7 @@
 #include "base/command_line.h"
 #include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
+#include "base/memory/weak_ptr.h"
 #include "build/build_config.h"
 #include "content/public/browser/web_contents.h"
 #include "content/public/browser/web_contents_delegate.h"
@@ -45,7 +46,11 @@ class CastWindowAndroid : public content::WebContentsDelegate,
   virtual ~CastWindowAndroid();
 
   void LoadURL(const GURL& url);
+  // Calls RVH::ClosePage() and waits for acknowledgement before closing/
+  // deleting the window.
   void Close();
+  // Destroys this window immediately.
+  void Destroy();
 
   // Registers the JNI methods for CastWindowAndroid.
   static bool RegisterJni(JNIEnv* env);
@@ -81,6 +86,8 @@ class CastWindowAndroid : public content::WebContentsDelegate,
   base::android::ScopedJavaGlobalRef<jobject> java_object_;
   scoped_ptr<content::WebContents> web_contents_;
 
+  base::WeakPtrFactory<CastWindowAndroid> weak_factory_;
+
   DISALLOW_COPY_AND_ASSIGN(CastWindowAndroid);
 };
 

chromecast/shell/browser/android/cast_window_manager.cc

@@ -65,11 +65,15 @@ jlong LaunchCastWindow(JNIEnv* env, jclass clazz, jstring jurl) {
           url));
 }
 
-void StopCastWindow(JNIEnv* env, jclass clazz, jlong nativeCastWindow) {
+void StopCastWindow(JNIEnv* env, jclass clazz,
+                    jlong nativeCastWindow, jboolean gracefully) {
   CastWindowAndroid* window =
       reinterpret_cast<CastWindowAndroid*>(nativeCastWindow);
   DCHECK(window);
-  window->Close();
+  if (gracefully)
+    window->Close();
+  else
+    window->Destroy();
 }
 
 void EnableDevTools(JNIEnv* env, jclass clazz, jboolean enable) {

chromecast/shell/browser/cast_browser_context.cc

@@ -5,6 +5,7 @@
 #include "chromecast/shell/browser/cast_browser_context.h"
 
 #include "base/command_line.h"
+#include "base/files/file_util.h"
 #include "base/macros.h"
 #include "base/path_service.h"
 #include "chromecast/common/cast_paths.h"