Execute operations of ChildProcessLauncher on launcher thread

content/public/android/java/src/org/chromium/content/browser/BindingManagerImpl.java

Index: content/public/android/java/src/org/chromium/content/browser/BindingManagerImpl.java
diff --git a/content/public/android/java/src/org/chromium/content/browser/BindingManagerImpl.java b/content/public/android/java/src/org/chromium/content/browser/BindingManagerImpl.java
index 2eaf20eb1a23a47564349189b4176f946254269f..8008d8f48f91e2db2acb142f046b7fe665b33837 100644
--- a/content/public/android/java/src/org/chromium/content/browser/BindingManagerImpl.java
+++ b/content/public/android/java/src/org/chromium/content/browser/BindingManagerImpl.java
@@ -40,11 +40,14 @@ class BindingManagerImpl implements BindingManager {
     private final long mRemoveStrongBindingDelay;
     private final boolean mIsLowMemoryDevice;
 
-    private static class ModerateBindingPool
-            extends LruCache<Integer, ManagedConnection> implements ComponentCallbacks2 {
+    interface LauncherThreadExecutor {
+        void execute(Runnable runnable);
+        void executeDelayed(Runnable runnable, long delayInMS);
+    }
+
+    private class ModerateBindingPool extends LruCache<Integer, ChildProcessConnection> {

[Yaron, 2015/09/14 22:30:59]

Can you add a brief comment on this? It should explain that this lives on
ProcessLauncher thread and what it actually does.

[Jaekyun Seok (inactive), 2015/09/14 23:44:11]

Done.

         private final float mLowReduceRatio;
         private final float mHighReduceRatio;
-        private final Object mDelayedClearerLock = new Object();
         private Runnable mDelayedClearer;
         private final Handler mHandler = new Handler(ThreadUtils.getUiThreadLooper());
 
@@ -55,34 +58,9 @@ class BindingManagerImpl implements BindingManager {
             mHighReduceRatio = highReduceRatio;
         }
 
-        @Override
-        public void onTrimMemory(int level) {
-            Log.i(TAG, "onTrimMemory: level=%d, size=%d", level, size());
-            if (size() > 0) {
-                if (level <= TRIM_MEMORY_RUNNING_MODERATE) {
-                    reduce(mLowReduceRatio);
-                } else if (level <= TRIM_MEMORY_RUNNING_LOW) {
-                    reduce(mHighReduceRatio);
-                } else if (level == TRIM_MEMORY_UI_HIDDEN) {
-                    // This will be handled by |mDelayedClearer|.
-                    return;
-                } else {
-                    evictAll();
-                }
-            }
-        }
-
-        @Override
-        public void onLowMemory() {
-            Log.i(TAG, "onLowMemory: evict %d bindings", size());
-            evictAll();
-        }
-
-        @Override
-        public void onConfigurationChanged(Configuration configuration) {}
-
         @TargetApi(Build.VERSION_CODES.JELLY_BEAN_MR1)
-        private void reduce(float reduceRatio) {
+        public void reduce(boolean useHighReduceRatio) {
+            final float reduceRatio = useHighReduceRatio ? mHighReduceRatio : mLowReduceRatio;
             int oldSize = size();
             int newSize = (int) (oldSize * (1f - reduceRatio));
             Log.i(TAG, "Reduce connections from %d to %d", oldSize, newSize);
@@ -94,7 +72,7 @@ class BindingManagerImpl implements BindingManager {
                 // Entries will be removed from the front because snapshot() returns ones ordered
                 // from least recently accessed to most recently accessed.
                 int count = 0;
-                for (Map.Entry<Integer, ManagedConnection> entry : snapshot().entrySet()) {
+                for (Map.Entry<Integer, ChildProcessConnection> entry : snapshot().entrySet()) {
                     remove(entry.getKey());
                     ++count;
                     if (count == oldSize - newSize) break;
@@ -102,70 +80,84 @@ class BindingManagerImpl implements BindingManager {
             }
         }
 
-        void addConnection(ManagedConnection managedConnection) {
-            ChildProcessConnection connection = managedConnection.mConnection;
+        public void addConnection(ChildProcessConnection connection) {
             if (connection != null && connection.isInSandbox()) {
-                managedConnection.addModerateBinding();
+                addModerateBinding(connection);
                 if (connection.isModerateBindingBound()) {
-                    put(connection.getServiceNumber(), managedConnection);
+                    put(connection.getServiceNumber(), connection);
                 } else {
                     remove(connection.getServiceNumber());
                 }
             }
         }
 
-        void removeConnection(ManagedConnection managedConnection) {
-            ChildProcessConnection connection = managedConnection.mConnection;
+        public void removeConnection(ChildProcessConnection connection) {
             if (connection != null && connection.isInSandbox()) {
                 remove(connection.getServiceNumber());
             }
         }
 
         @Override
-        protected void entryRemoved(boolean evicted, Integer key, ManagedConnection oldValue,
-                ManagedConnection newValue) {
-            if (oldValue != newValue) {
-                oldValue.removeModerateBinding();
-            }
+        protected void entryRemoved(boolean evicted, Integer key, ChildProcessConnection oldValue,
+                ChildProcessConnection newValue) {
+            if (oldValue != newValue) removeModerateBinding(oldValue);
         }
 
-        void onSentToBackground(final boolean onTesting) {
+        public void onSentToBackground(final boolean onTesting) {
             if (size() == 0) return;
-            synchronized (mDelayedClearerLock) {
-                mDelayedClearer = new Runnable() {
-                    @Override
-                    public void run() {
-                        synchronized (mDelayedClearerLock) {
+            mDelayedClearer = new Runnable() {
+                @Override
+                public void run() {
+                    mLauncherThreadExecutor.execute(new Runnable() {
+                        @Override
+                        public void run() {
                             if (mDelayedClearer == null) return;
                             mDelayedClearer = null;
+
+                            Log.i(TAG, "Release moderate connections: %d", size());
+                            if (!onTesting) {
+                                RecordHistogram.recordCountHistogram(
+                                        "Android.ModerateBindingCount", size());
+                            }
+                            evictAll();
                         }
-                        Log.i(TAG, "Release moderate connections: %d", size());
-                        if (!onTesting) {
-                            RecordHistogram.recordCountHistogram(
-                                    "Android.ModerateBindingCount", size());
-                        }
-                        evictAll();
-                    }
-                };
-                mHandler.postDelayed(mDelayedClearer, onTesting
-                                ? MODERATE_BINDING_POOL_CLEARER_DELAY_MILLIS_ON_TESTING
-                                : MODERATE_BINDING_POOL_CLEARER_DELAY_MILLIS);
-            }
+                    });
+                }
+            };
+            mHandler.postDelayed(mDelayedClearer, onTesting
+                            ? MODERATE_BINDING_POOL_CLEARER_DELAY_MILLIS_ON_TESTING
+                            : MODERATE_BINDING_POOL_CLEARER_DELAY_MILLIS);
         }
 
-        void onBroughtToForeground() {
-            synchronized (mDelayedClearerLock) {
-                if (mDelayedClearer == null) return;
-                mHandler.removeCallbacks(mDelayedClearer);
-                mDelayedClearer = null;
-            }
+        public void onBroughtToForeground() {
+            if (mDelayedClearer == null) return;
+            mHandler.removeCallbacks(mDelayedClearer);
+            mDelayedClearer = null;
+        }
+
+        private void removeModerateBinding(ChildProcessConnection connection) {
+            if (connection == null || !connection.isModerateBindingBound()) return;
+            connection.removeModerateBinding();
+        }
+
+        private void addModerateBinding(ChildProcessConnection connection) {
+            if (connection == null) return;
+
+            connection.addModerateBinding();
         }
     }
 
-    private final Object mModerateBindingPoolLock = new Object();
     private ModerateBindingPool mModerateBindingPool;
 
     /**
+     * Interface to listen to events related strong binding.
+     */
+    interface StrongBindingEventListener {
+        void onAdded(ChildProcessConnection managedConnection);
+        void onRemoved(ChildProcessConnection connection, boolean wasBoundForBackgroundPeriod);
+    }
+
+    /**
      * Wraps ChildProcessConnection keeping track of additional information needed to manage the
      * bindings of the connection. The reference to ChildProcessConnection is cleared when the
      * connection goes away, but ManagedConnection itself is kept (until overwritten by a new entry
@@ -173,7 +165,7 @@ class BindingManagerImpl implements BindingManager {
      */
     private class ManagedConnection {
         // Set in constructor, cleared in clearConnection().
-        private ChildProcessConnection mConnection;
+        private volatile ChildProcessConnection mConnection;
 
         // True iff there is a strong binding kept on the service because it is working in
         // foreground.
@@ -186,6 +178,8 @@ class BindingManagerImpl implements BindingManager {
         // When mConnection is cleared, oom binding status is stashed here.
         private boolean mWasOomProtected;
 
+        private StrongBindingEventListener mStrongBindingEventListener;
+
         /** Removes the initial service binding. */
         private void removeInitialBinding() {
             if (mConnection == null || !mConnection.isInitialBindingBound()) return;
@@ -194,88 +188,66 @@ class BindingManagerImpl implements BindingManager {
 
         /** Adds a strong service binding. */
         private void addStrongBinding() {
-            ChildProcessConnection connection = mConnection;
-            if (connection == null) return;
+            if (mConnection == null) return;
 
-            connection.addStrongBinding();
-            ModerateBindingPool moderateBindingPool;
-            synchronized (mModerateBindingPoolLock) {
-                moderateBindingPool = mModerateBindingPool;
-            }
-            if (moderateBindingPool != null) moderateBindingPool.removeConnection(this);
+            mConnection.addStrongBinding();
+            mStrongBindingEventListener.onAdded(mConnection);
         }
 
         /** Removes a strong service binding. */
-        private void removeStrongBinding(final boolean keepsAsModerate) {
-            final ChildProcessConnection connection = mConnection;
+        private void removeStrongBinding(final boolean wasBoundForBackgroundPeriod) {
             // We have to fail gracefully if the strong binding is not present, as on low-end the
             // binding could have been removed by dropOomBindings() when a new service was started.
-            if (connection == null || !connection.isStrongBindingBound()) return;
+            if (mConnection == null || !mConnection.isStrongBindingBound()) return;
 
             // This runnable performs the actual unbinding. It will be executed synchronously when
             // on low-end devices and posted with a delay otherwise.
-            Runnable doUnbind = new Runnable() {
+            final Runnable doUnbind = new Runnable() {
                 @Override
                 public void run() {
-                    if (connection.isStrongBindingBound()) {
-                        connection.removeStrongBinding();
-                        ModerateBindingPool moderateBindingPool;
-                        synchronized (mModerateBindingPoolLock) {
-                            moderateBindingPool = mModerateBindingPool;
-                        }
-                        if (moderateBindingPool != null && !connection.isStrongBindingBound()
-                                && keepsAsModerate) {
-                            moderateBindingPool.addConnection(ManagedConnection.this);
-                        }
-                    }
+                    if (mConnection == null || !mConnection.isStrongBindingBound()) return;
+                    mConnection.removeStrongBinding();
+                    mStrongBindingEventListener.onRemoved(mConnection, wasBoundForBackgroundPeriod);
                 }
             };
 
             if (mIsLowMemoryDevice) {
                 doUnbind.run();
             } else {
-                ThreadUtils.postOnUiThreadDelayed(doUnbind, mRemoveStrongBindingDelay);
+                mLauncherThreadExecutor.executeDelayed(new Runnable() {
+                    @Override
+                    public void run() {
+                        doUnbind.run();
+                    }
+                }, mRemoveStrongBindingDelay);
             }
         }
 
-        /** Removes the moderate service binding. */
-        private void removeModerateBinding() {
-            if (mConnection == null || !mConnection.isModerateBindingBound()) return;
-            mConnection.removeModerateBinding();
-        }
-
-        /** Adds the moderate service binding. */
-        private void addModerateBinding() {
-            ChildProcessConnection connection = mConnection;
-            if (connection == null) return;
-
-            connection.addModerateBinding();
-        }
-
         /**
          * Drops the service bindings. This is used on low-end to drop bindings of the current
          * service when a new one is used in foreground.
          */
-        private void dropBindings() {
+        public void dropBindings() {
             assert mIsLowMemoryDevice;
-            ChildProcessConnection connection = mConnection;
-            if (connection == null) return;
+            if (mConnection == null) return;
 
-            connection.dropOomBindings();
+            mConnection.dropOomBindings();
         }
 
-        ManagedConnection(ChildProcessConnection connection) {
+        ManagedConnection(ChildProcessConnection connection,
+                StrongBindingEventListener strongBindingEventListener) {
             mConnection = connection;
+            mStrongBindingEventListener = strongBindingEventListener;
         }
 
         /**
          * Sets the visibility of the service, adding or removing the strong binding as needed.
          */
-        void setInForeground(boolean nextInForeground) {
+        public void setInForeground(boolean nextInForeground) {
             if (!mInForeground && nextInForeground) {
                 addStrongBinding();
             } else if (mInForeground && !nextInForeground) {
-                removeStrongBinding(true);
+                removeStrongBinding(false);
             }
 
             mInForeground = nextInForeground;
@@ -284,7 +256,7 @@ class BindingManagerImpl implements BindingManager {
         /**
          * Removes the initial binding.
          */
-        void determinedVisibility() {
+        public void determinedVisibility() {
             removeInitialBinding();
         }
 
@@ -292,37 +264,39 @@ class BindingManagerImpl implements BindingManager {
          * Sets or removes additional binding when the service is main service during the embedder
          * background period.
          */
-        void setBoundForBackgroundPeriod(boolean nextBound) {
+        public void setBoundForBackgroundPeriod(boolean nextBound) {
             if (!mBoundForBackgroundPeriod && nextBound) {
                 addStrongBinding();
             } else if (mBoundForBackgroundPeriod && !nextBound) {
-                removeStrongBinding(false);
+                removeStrongBinding(true);
             }
 
             mBoundForBackgroundPeriod = nextBound;
         }
 
-        boolean isOomProtected() {
+        /** This may be called from any thread. */
+        public boolean isOomProtected() {
             // When a process crashes, we can be queried about its oom status before or after the
             // connection is cleared. For the latter case, the oom status is stashed in
             // mWasOomProtected.
-            return mConnection != null
-                    ? mConnection.isOomProtectedOrWasWhenDied() : mWasOomProtected;
+            ChildProcessConnection connection = mConnection;
+            if (connection == null) return mWasOomProtected;
+
+            return connection.isOomProtectedOrWasWhenDied();
         }
 
-        void clearConnection() {
+        public void clearConnection() {
+            if (mConnection == null) return;
             mWasOomProtected = mConnection.isOomProtectedOrWasWhenDied();
-            ModerateBindingPool moderateBindingPool;
-            synchronized (mModerateBindingPoolLock) {
-                moderateBindingPool = mModerateBindingPool;
-            }
-            if (moderateBindingPool != null) moderateBindingPool.removeConnection(this);
             mConnection = null;
         }
 
-        /** @return true iff the reference to the connection is no longer held */
+        /**
+         * This may be called from any thread.
+         * @return true iff the reference to the connection is no longer held
+         */
         @VisibleForTesting
-        boolean isConnectionCleared() {
+        public boolean isConnectionCleared() {
             return mConnection == null;
         }
     }
@@ -337,30 +311,47 @@ class BindingManagerImpl implements BindingManager {
     // renderer process at a time is protected from oom killing.
     private ManagedConnection mLastInForeground;
 
-    // Synchronizes operations that access mLastInForeground: setInForeground() and
-    // addNewConnection().
-    private final Object mLastInForegroundLock = new Object();
-
     // The connection bound with additional binding in onSentToBackground().
     private ManagedConnection mBoundForBackgroundPeriod;
 
     // Whether this instance is used on testing.
     private final boolean mOnTesting;
 
+    // Executor that executes a task on LauncherThread.
+    private final LauncherThreadExecutor mLauncherThreadExecutor;
+
+    private final Object mThreadIdLock = new Object();
+    private Long mThreadId;
+
+    void checkCalledOnProcessLauncherThread() {
+        if (mOnTesting) return;
+
+        synchronized (mThreadIdLock) {
+            long currentThreadId = Thread.currentThread().getId();
+            if (mThreadId == null) {
+                mThreadId = currentThreadId;
+            } else if (mThreadId != currentThreadId) {
+                throw new IllegalStateException(
+                        "Method is not called on valid thread: " + Thread.currentThread());
+            }
+        }
+    }
+
     /**
      * The constructor is private to hide parameters exposed for testing from the regular consumer.
      * Use factory methods to create an instance.
      */
-    private BindingManagerImpl(
-            boolean isLowMemoryDevice, long removeStrongBindingDelay, boolean onTesting) {
+    private BindingManagerImpl(boolean isLowMemoryDevice, long removeStrongBindingDelay,
+            boolean onTesting, LauncherThreadExecutor executor) {
         mIsLowMemoryDevice = isLowMemoryDevice;
         mRemoveStrongBindingDelay = removeStrongBindingDelay;
         mOnTesting = onTesting;
+        mLauncherThreadExecutor = executor;
     }
 
-    public static BindingManagerImpl createBindingManager() {
+    public static BindingManagerImpl createBindingManager(LauncherThreadExecutor executor) {
         return new BindingManagerImpl(
-                SysUtils.isLowEndDevice(), DETACH_AS_ACTIVE_HIGH_END_DELAY_MILLIS, false);
+                SysUtils.isLowEndDevice(), DETACH_AS_ACTIVE_HIGH_END_DELAY_MILLIS, false, executor);
     }
 
     /**
@@ -369,20 +360,56 @@ class BindingManagerImpl implements BindingManager {
      * @param isLowEndDevice true iff the created instance should apply low-end binding policies
      */
     public static BindingManagerImpl createBindingManagerForTesting(boolean isLowEndDevice) {
-        return new BindingManagerImpl(isLowEndDevice, 0, true);
+        LauncherThreadExecutor executor = new LauncherThreadExecutor() {
+            @Override
+            public void execute(Runnable runnable) {
+                ThreadUtils.runOnUiThread(runnable);
+            }
+
+            @Override
+            public void executeDelayed(Runnable runnable, long delayInMS) {
+                ThreadUtils.postOnUiThreadDelayed(runnable, delayInMS);
+            }
+        };
+        return new BindingManagerImpl(isLowEndDevice, 0, true, executor);
     }
 
     @Override
     public void addNewConnection(int pid, ChildProcessConnection connection) {
+        checkCalledOnProcessLauncherThread();
+
         // This will reset the previous entry for the pid in the unlikely event of the OS
         // reusing renderer pids.
         synchronized (mManagedConnections) {
-            mManagedConnections.put(pid, new ManagedConnection(connection));
+            StrongBindingEventListener listener = new StrongBindingEventListener() {
+                @Override
+                public void onAdded(ChildProcessConnection connection) {
+                    checkCalledOnProcessLauncherThread();
+
+                    if (mModerateBindingPool != null) {
+                        mModerateBindingPool.removeConnection(connection);
+                    }
+                }
+
+                @Override
+                public void onRemoved(
+                        ChildProcessConnection connection, boolean wasBoundForBackgroundPeriod) {
+                    checkCalledOnProcessLauncherThread();
+
+                    if (mModerateBindingPool != null && !connection.isStrongBindingBound()
+                            && !wasBoundForBackgroundPeriod) {
+                        mModerateBindingPool.addConnection(connection);
+                    }
+                }
+            };
+            mManagedConnections.put(pid, new ManagedConnection(connection, listener));
         }
     }
 
     @Override
     public void setInForeground(int pid, boolean inForeground) {
+        checkCalledOnProcessLauncherThread();
+
         ManagedConnection managedConnection;
         synchronized (mManagedConnections) {
             managedConnection = mManagedConnections.get(pid);
@@ -393,19 +420,19 @@ class BindingManagerImpl implements BindingManager {
             return;
         }
 
-        synchronized (mLastInForegroundLock) {
-            if (inForeground && mIsLowMemoryDevice && mLastInForeground != null
-                    && mLastInForeground != managedConnection) {
-                mLastInForeground.dropBindings();
-            }
-
-            managedConnection.setInForeground(inForeground);
-            if (inForeground) mLastInForeground = managedConnection;
+        if (inForeground && mIsLowMemoryDevice && mLastInForeground != null
+                && mLastInForeground != managedConnection) {
+            mLastInForeground.dropBindings();
         }
+
+        managedConnection.setInForeground(inForeground);
+        if (inForeground) mLastInForeground = managedConnection;
     }
 
     @Override
     public void determinedVisibility(int pid) {
+        checkCalledOnProcessLauncherThread();
+
         ManagedConnection managedConnection;
         synchronized (mManagedConnections) {
             managedConnection = mManagedConnections.get(pid);
@@ -422,35 +449,32 @@ class BindingManagerImpl implements BindingManager {
 
     @Override
     public void onSentToBackground() {
+        checkCalledOnProcessLauncherThread();
+
         assert mBoundForBackgroundPeriod == null;
-        synchronized (mLastInForegroundLock) {
-            // mLastInForeground can be null at this point as the embedding application could be
-            // used in foreground without spawning any renderers.
-            if (mLastInForeground != null) {
-                mLastInForeground.setBoundForBackgroundPeriod(true);
-                mBoundForBackgroundPeriod = mLastInForeground;
-            }
-        }
-        ModerateBindingPool moderateBindingPool;
-        synchronized (mModerateBindingPoolLock) {
-            moderateBindingPool = mModerateBindingPool;
+
+        // mLastInForeground can be null at this point as the embedding application could be
+        // used in foreground without spawning any renderers.
+        if (mLastInForeground != null) {
+            mLastInForeground.setBoundForBackgroundPeriod(true);
+            mBoundForBackgroundPeriod = mLastInForeground;
         }
-        if (moderateBindingPool != null) moderateBindingPool.onSentToBackground(mOnTesting);
+
+        if (mModerateBindingPool != null) mModerateBindingPool.onSentToBackground(mOnTesting);
     }
 
     @Override
     public void onBroughtToForeground() {
+        checkCalledOnProcessLauncherThread();
+
         if (mBoundForBackgroundPeriod != null) {
             mBoundForBackgroundPeriod.setBoundForBackgroundPeriod(false);
             mBoundForBackgroundPeriod = null;
         }
-        ModerateBindingPool moderateBindingPool;
-        synchronized (mModerateBindingPoolLock) {
-            moderateBindingPool = mModerateBindingPool;
-        }
-        if (moderateBindingPool != null) moderateBindingPool.onBroughtToForeground();
+        if (mModerateBindingPool != null) mModerateBindingPool.onBroughtToForeground();
     }
 
+    /** This may be called from any thread. */
     @Override
     public boolean isOomProtected(int pid) {
         // In the unlikely event of the OS reusing renderer pid, the call will refer to the most
@@ -464,45 +488,94 @@ class BindingManagerImpl implements BindingManager {
     }
 
     @Override
-    public void clearConnection(int pid) {
+    public void clearConnection(final int pid) {

[Yaron, 2015/09/14 22:30:59]

why is this final now?

[Jaekyun Seok (inactive), 2015/09/14 23:44:11]

Removed.

+        checkCalledOnProcessLauncherThread();
+
         ManagedConnection managedConnection;
         synchronized (mManagedConnections) {
             managedConnection = mManagedConnections.get(pid);
         }
-        if (managedConnection != null) managedConnection.clearConnection();
+        // TODO: we need to find a way to clean up dead connections in mManagedConnections.
+        if (managedConnection != null) {
+            if (mModerateBindingPool != null) {
+                mModerateBindingPool.removeConnection(managedConnection.mConnection);
+            }
+            managedConnection.clearConnection();
+        }
     }
 
-    /** @return true iff the connection reference is no longer held */
+    /**
+     * This may be called from any thread.
+     * @return true iff the connection reference is no longer held
+     */
     @VisibleForTesting
     public boolean isConnectionCleared(int pid) {
         synchronized (mManagedConnections) {
-            return mManagedConnections.get(pid).isConnectionCleared();
+            ManagedConnection managedConnection = mManagedConnections.get(pid);
+            return managedConnection == null || managedConnection.isConnectionCleared();
         }
     }
 
     @Override
     public void startModerateBindingManagement(
             Context context, int maxSize, float lowReduceRatio, float highReduceRatio) {
-        synchronized (mModerateBindingPoolLock) {
-            if (mIsLowMemoryDevice || mModerateBindingPool != null) return;
+        checkCalledOnProcessLauncherThread();
+
+        if (mIsLowMemoryDevice || mModerateBindingPool != null) return;
+
+        Log.i(TAG, "Moderate binding enabled: maxSize=%d lowReduceRatio=%f highReduceRatio=%f",
+                maxSize, lowReduceRatio, highReduceRatio);
+        mModerateBindingPool = new ModerateBindingPool(maxSize, lowReduceRatio, highReduceRatio);
+        if (context != null) {
+            context.registerComponentCallbacks(new ComponentCallbacks2() {
+                @Override
+                public void onTrimMemory(final int level) {
+                    mLauncherThreadExecutor.execute(new Runnable() {
+                        @Override
+                        public void run() {
+                            Log.i(TAG, "onTrimMemory: level=%d, size=%d", level,
+                                    mModerateBindingPool.size());
+                            if (mModerateBindingPool.size() > 0) {
+                                if (level <= TRIM_MEMORY_RUNNING_MODERATE) {
+                                    mModerateBindingPool.reduce(false);
+                                } else if (level <= TRIM_MEMORY_RUNNING_LOW) {
+                                    mModerateBindingPool.reduce(true);
+                                } else if (level == TRIM_MEMORY_UI_HIDDEN) {
+                                    // This will be handled by onSentToBackground().
+                                    return;
+                                } else {
+                                    mModerateBindingPool.evictAll();
+                                }
+                            }
+                        }
+                    });
+                }
 
-            Log.i(TAG, "Moderate binding enabled: maxSize=%d lowReduceRatio=%f highReduceRatio=%f",
-                    maxSize, lowReduceRatio, highReduceRatio);
-            mModerateBindingPool =
-                    new ModerateBindingPool(maxSize, lowReduceRatio, highReduceRatio);
-            if (context != null) context.registerComponentCallbacks(mModerateBindingPool);
+                @Override
+                public void onLowMemory() {
+                    mLauncherThreadExecutor.execute(new Runnable() {
+                        @Override
+                        public void run() {
+                            Log.i(TAG, "onLowMemory: evict %d bindings",
+                                    mModerateBindingPool.size());
+                            mModerateBindingPool.evictAll();
+                        }
+                    });
+                }
+
+                @Override
+                public void onConfigurationChanged(Configuration configuration) {}
+            });
         }
     }
 
     @Override
     public void releaseAllModerateBindings() {
-        ModerateBindingPool moderateBindingPool;
-        synchronized (mModerateBindingPoolLock) {
-            moderateBindingPool = mModerateBindingPool;
-        }
-        if (moderateBindingPool != null) {
-            Log.i(TAG, "Release all moderate bindings: %d", moderateBindingPool.size());
-            moderateBindingPool.evictAll();
+        checkCalledOnProcessLauncherThread();
+
+        if (mModerateBindingPool != null) {
+            Log.i(TAG, "Release all moderate bindings: %d", mModerateBindingPool.size());
+            mModerateBindingPool.evictAll();
         }
     }
 }