[Suggestions UI] Drop Bitmap references from articles under memory pressure.

chrome/android/java/src/org/chromium/chrome/browser/ChromeActivity.java

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 package org.chromium.chrome.browser;
 
 import android.annotation.SuppressLint;
 import android.annotation.TargetApi;
 import android.app.Activity;
 import android.app.SearchManager;
@@ skipping 28 matching lines @@
 import android.view.accessibility.AccessibilityManager.AccessibilityStateChangeListener;
 import android.view.accessibility.AccessibilityManager.TouchExplorationStateChangeListener;
 
 import org.chromium.base.ActivityState;
 import org.chromium.base.ApiCompatibilityUtils;
 import org.chromium.base.ApplicationStatus;
 import org.chromium.base.BaseSwitches;
 import org.chromium.base.Callback;
 import org.chromium.base.CommandLine;
 import org.chromium.base.ContextUtils;
+import org.chromium.base.DiscardableReferencePool;
 import org.chromium.base.SysUtils;
 import org.chromium.base.TraceEvent;
 import org.chromium.base.VisibleForTesting;
 import org.chromium.base.metrics.RecordHistogram;
 import org.chromium.base.metrics.RecordUserAction;
 import org.chromium.chrome.R;
 import org.chromium.chrome.browser.IntentHandler.IntentHandlerDelegate;
 import org.chromium.chrome.browser.IntentHandler.TabOpenType;
 import org.chromium.chrome.browser.appmenu.AppMenu;
 import org.chromium.chrome.browser.appmenu.AppMenuHandler;
@@ skipping 206 matching lines @@
     private BottomSheetContentController mBottomSheetContentController;
     private FadingBackgroundView mFadingBackgroundView;
 
     // Time in ms that it took took us to inflate the initial layout
     private long mInflateInitialLayoutDurationMs;
 
     private int mUiMode;
     private int mScreenWidthDp;
     private Runnable mRecordMultiWindowModeScreenWidthRunnable;
 
+    private final DiscardableReferencePool mReferencePool = new DiscardableReferencePool();
+
     private AssistStatusHandler mAssistStatusHandler;
 
     // A set of views obscuring all tabs. When this set is nonempty,
     // all tab content will be hidden from the accessibility tree.
     private Set<View> mViewsObscuringAllTabs = new HashSet<>();
 
     // See enableHardwareAcceleration()
     private boolean mSetWindowHWA;
 
     // Skips capturing screenshot for testing purpose.
@@ skipping 1486 matching lines @@
             return;
         }
 
         if (mContextualSearchManager != null && mContextualSearchManager.onBackPressed()) return;
 
         if (handleBackPressed()) return;
 
         super.onBackPressed();
     }
 
+    @Override
+    public void onTrimMemory(int level) {
+        super.onTrimMemory(level);
+        // The conditions are expressed using ranges to capture intermediate levels possibly added
+        // to the API in the future.
+        if ((level >= TRIM_MEMORY_RUNNING_LOW && level < TRIM_MEMORY_UI_HIDDEN)
+                || level >= TRIM_MEMORY_MODERATE) {
+            mReferencePool.drain();
+        }
+    }
 
     private ContentViewCore getContentViewCore() {
         Tab tab = getActivityTab();
         if (tab == null) return null;
         return tab.getContentViewCore();
     }
 
     @Override
     public void createContextualSearchTab(String searchUrl) {
         Tab currentTab = getActivityTab();
@@ skipping 405 matching lines @@
      */
     public void onExitVr() {}
 
     /**
      * Whether this Activity supports moving a {@link Tab} to the
      * {@link FullscreenWebContentsActivity} when it enters fullscreen.
      */
     public boolean supportsFullscreenActivity() {
         return false;
     }
+
+    /**
+     * @return the reference pool for this activity.
+     */
+    public DiscardableReferencePool getReferencePool() {
+        return mReferencePool;
+    }
 }