Make ActivityWindowAndroid per-activity

This is to solve the general perf problem of per-webview
ActivityWindowAndroid when there are a lot of webviews in an activity.
It is kept in a WeakHashMap, and ActivityWindowAndroid only weakly holds
the Activity, to ensure Activity can still be gc-ed.
ActivityWindowAndroid.destroy is called by CleanupReference.

Also make WindowAndroid global and leaking. This is ok since it only uses
the Application.

BUG=487487

Review URL: https://codereview.chromium.org/1138113004

Cr-Commit-Position: refs/heads/master@{#330087}

android_webview/java/src/org/chromium/android_webview/AwContents.java

@@ -77,6 +77,7 @@ import java.net.URL;
 import java.util.HashMap;
 import java.util.Locale;
 import java.util.Map;
+import java.util.WeakHashMap;
 import java.util.concurrent.Callable;
 
 /**
@@ -207,7 +208,7 @@ public class AwContents implements SmartClipProvider,
     private final Context mContext;
     private final int mAppTargetSdkVersion;
     private ContentViewCore mContentViewCore;
-    private WindowAndroid mWindowAndroid;
+    private WindowAndroidWrapper mWindowAndroid;
     private WebContents mWebContents;
     private NavigationController mNavigationController;
     private final AwContentsClient mContentsClient;
@@ -287,16 +288,13 @@ public class AwContents implements SmartClipProvider,
 
     private static final class DestroyRunnable implements Runnable {
         private final long mNativeAwContents;
-        private final WindowAndroid mWindowAndroid;
 
-        private DestroyRunnable(long nativeAwContents, WindowAndroid windowAndroid) {
+        private DestroyRunnable(long nativeAwContents) {
             mNativeAwContents = nativeAwContents;
-            mWindowAndroid = windowAndroid;
         }
         @Override
         public void run() {
             nativeDestroy(mNativeAwContents);
-            mWindowAndroid.destroy();
         }
     }
 
@@ -848,6 +846,60 @@ public class AwContents implements SmartClipProvider,
         mContainerView.requestLayout();
     }
 
+    // This class destroys the WindowAndroid when after it is gc-ed.
+    private static class WindowAndroidWrapper {
+        private final WindowAndroid mWindowAndroid;
+        private final CleanupReference mCleanupReference;
+
+        private static final class DestroyRunnable implements Runnable {
+            private final WindowAndroid mWindowAndroid;
+            private DestroyRunnable(WindowAndroid windowAndroid) {
+                mWindowAndroid = windowAndroid;
+            }
+            @Override
+            public void run() {
+                mWindowAndroid.destroy();
+            }
+        }
+
+        public WindowAndroidWrapper(WindowAndroid windowAndroid) {
+            mWindowAndroid = windowAndroid;
+            mCleanupReference =
+                    new CleanupReference(this, new DestroyRunnable(windowAndroid));
+        }
+
+        public WindowAndroid getWindowAndroid() {
+            return mWindowAndroid;
+        }
+    }
+    private static WindowAndroidWrapper sCachedWindowAndroid;
+    private static WeakHashMap<Activity, WindowAndroidWrapper> sActivityWindowMap;
+
+    // getWindowAndroid is only called on UI thread, so there are no threading issues with lazy
+    // initialization.
+    @SuppressFBWarnings("LI_LAZY_INIT_STATIC")
+    private static WindowAndroidWrapper getWindowAndroid(Context context) {
+        // TODO(boliu): WebView does not currently initialize ApplicationStatus, crbug.com/470582.
+        Activity activity = ContentViewCore.activityFromContext(context);
+        if (activity == null) {
+            if (sCachedWindowAndroid == null) {
+                sCachedWindowAndroid = new WindowAndroidWrapper(
+                        new WindowAndroid(context.getApplicationContext()));
+            }
+            return sCachedWindowAndroid;
+        }
+
+        if (sActivityWindowMap == null) sActivityWindowMap = new WeakHashMap<>();
+        WindowAndroidWrapper activityWindowAndroid = sActivityWindowMap.get(activity);
+        if (activityWindowAndroid == null) {
+            final boolean listenToActivityState = false;
+            activityWindowAndroid = new WindowAndroidWrapper(
+                    new ActivityWindowAndroid(activity, listenToActivityState));
+            sActivityWindowMap.put(activity, activityWindowAndroid);
+        }
+        return activityWindowAndroid;
+    }
+
     /* Common initialization routine for adopting a native AwContents instance into this
      * java instance.
      *
@@ -871,15 +923,10 @@ public class AwContents implements SmartClipProvider,
 
         WebContents webContents = nativeGetWebContents(mNativeAwContents);
 
-        // WebView does not currently initialize ApplicationStatus, crbug.com/470582.
-        final boolean listenToActivityState = false;
-        Activity activity = ContentViewCore.activityFromContext(mContext);
-        mWindowAndroid = activity != null
-                ? new ActivityWindowAndroid(activity, listenToActivityState)
-                : new WindowAndroid(mContext.getApplicationContext());
-        mContentViewCore = createAndInitializeContentViewCore(
-                mContainerView, mContext, mInternalAccessAdapter, webContents,
-                new AwGestureStateListener(), mContentViewClient, mZoomControls, mWindowAndroid);
+        mWindowAndroid = getWindowAndroid(mContext);
+        mContentViewCore = createAndInitializeContentViewCore(mContainerView, mContext,
+                mInternalAccessAdapter, webContents, new AwGestureStateListener(),
+                mContentViewClient, mZoomControls, mWindowAndroid.getWindowAndroid());
         nativeSetJavaPeers(mNativeAwContents, this, mWebContentsDelegate, mContentsClientBridge,
                 mIoThreadClient, mInterceptNavigationDelegate);
         mWebContents = mContentViewCore.getWebContents();
@@ -892,7 +939,7 @@ public class AwContents implements SmartClipProvider,
         // The native side object has been bound to this java instance, so now is the time to
         // bind all the native->java relationships.
         mCleanupReference =
-                new CleanupReference(this, new DestroyRunnable(mNativeAwContents, mWindowAndroid));
+                new CleanupReference(this, new DestroyRunnable(mNativeAwContents));
     }
 
     private void installWebContentsObserver() {
@@ -2452,7 +2499,7 @@ public class AwContents implements SmartClipProvider,
 
     @CalledByNative
     private void postInvalidateOnAnimation() {
-        if (!mWindowAndroid.isInsideVSync()) {
+        if (!mWindowAndroid.getWindowAndroid().isInsideVSync()) {
             mContainerView.postInvalidateOnAnimation();
         } else {
             mContainerView.invalidate();