aw: Page visiblity behind switch

Enable page visibility behind a command line switch. There should be
no change in behavior if enable-page-visibility switch is missing.

When it's added:
* Visibility is changed to
  (view visible) && (!attached or window visible) && (!onPause-ed)
  The existing implementation is simply !onPaused.
* Pass page visibility signal into blink, and in turn, the compositor.

BUG=520089

Review URL: https://codereview.chromium.org/1291653004

Cr-Commit-Position: refs/heads/master@{#343396}

android_webview/common/aw_switches.cc

@@ -6,6 +6,7 @@
 
 namespace switches {
 
+const char kEnablePageVisibility[] = "enable-page-visibility";
 const char kUseInProcCommandBuffer[] = "use-in-proc-command-buffer";
 
 }  // namespace switches

android_webview/common/aw_switches.h

@@ -7,6 +7,7 @@
 
 namespace switches {
 
+extern const char kEnablePageVisibility[];
 extern const char kUseInProcCommandBuffer[];
 
 }  // namespace switches

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

@@ -43,6 +43,7 @@
 
 import org.chromium.android_webview.permission.AwGeolocationCallback;
 import org.chromium.android_webview.permission.AwPermissionRequest;
+import org.chromium.base.CommandLine;
 import org.chromium.base.LocaleUtils;
 import org.chromium.base.ThreadUtils;
 import org.chromium.base.TraceEvent;
@@ -106,6 +107,9 @@ public class AwContents implements SmartClipProvider,
     private static final boolean FORCE_AUXILIARY_BITMAP_RENDERING =
             "goldfish".equals(Build.HARDWARE);
 
+    // Matches kEnablePageVisibility.
+    private static final String ENABLE_PAGE_VISIBILITY = "enable-page-visibility";
+
     /**
      * WebKit hit test related data structure. These are used to implement
      * getHitTestResult, requestFocusNodeHref, requestImageRef methods in WebView.
@@ -233,10 +237,15 @@ public abstract static class VisualStateCallback {
     private final AwSettings mSettings;
     private final ScrollAccessibilityHelper mScrollAccessibilityHelper;
 
+    // Visibility related state.
+    private final boolean mEnablePageVisibility;
     private boolean mIsPaused;
     private boolean mIsViewVisible;
     private boolean mIsWindowVisible;
     private boolean mIsAttachedToWindow;
+    // Visiblity state of |mContentViewCore|.
+    private boolean mIsContentViewCoreVisible;
+
     private Bitmap mFavicon;
     private boolean mHasRequestedVisitedHistoryFromClient;
     // TODO(boliu): This should be in a global context, not per webview.
@@ -716,6 +725,7 @@ public void onGestureZoomSupportChanged(
         mScrollOffsetManager = dependencyFactory.createScrollOffsetManager(
                 new AwScrollOffsetManagerDelegate(), new OverScroller(mContext));
         mScrollAccessibilityHelper = new ScrollAccessibilityHelper(mContainerView);
+        mEnablePageVisibility = CommandLine.getInstance().hasSwitch(ENABLE_PAGE_VISIBILITY);
 
         setOverScrollMode(mContainerView.getOverScrollMode());
         setScrollBarStyle(mInternalAccessAdapter.super_getScrollBarStyle());
@@ -963,7 +973,7 @@ mInternalAccessAdapter, webContents, new AwGestureStateListener(),
         installWebContentsObserver();
         mSettings.setWebContents(webContents);
         nativeSetDipScale(mNativeAwContents, (float) mDIPScale);
-        mContentViewCore.onShow();
+        updateContentViewCoreVisibility();
 
         // The native side object has been bound to this java instance, so now is the time to
         // bind all the native->java relationships.
@@ -1763,7 +1773,7 @@ public void onPause() {
         if (mIsPaused || isDestroyed()) return;
         mIsPaused = true;
         nativeSetIsPaused(mNativeAwContents, mIsPaused);
-        mContentViewCore.onHide();
+        updateContentViewCoreVisibility();
     }
 
     /**
@@ -1774,7 +1784,7 @@ public void onResume() {
         if (!mIsPaused || isDestroyed()) return;
         mIsPaused = false;
         nativeSetIsPaused(mNativeAwContents, mIsPaused);
-        mContentViewCore.onShow();
+        updateContentViewCoreVisibility();
     }
 
     /**
@@ -2274,13 +2284,30 @@ public void onWindowVisibilityChanged(int visibility) {
     private void setViewVisibilityInternal(boolean visible) {
         mIsViewVisible = visible;
         if (!isDestroyed()) nativeSetViewVisibility(mNativeAwContents, mIsViewVisible);
+        updateContentViewCoreVisibility();
     }
 
     private void setWindowVisibilityInternal(boolean visible) {
         mInvalidateRootViewOnNextDraw |= Build.VERSION.SDK_INT <= Build.VERSION_CODES.LOLLIPOP
                 && visible && !mIsWindowVisible;
         mIsWindowVisible = visible;
         if (!isDestroyed()) nativeSetWindowVisibility(mNativeAwContents, mIsWindowVisible);
+        updateContentViewCoreVisibility();
+    }
+
+    private void updateContentViewCoreVisibility() {
+        if (isDestroyed()) return;
+        boolean contentViewCoreVisible = !mIsPaused;
+        if (mEnablePageVisibility) {
+            contentViewCoreVisible = contentViewCoreVisible && mIsWindowVisible && mIsViewVisible;
+        }
+
+        if (contentViewCoreVisible && !mIsContentViewCoreVisible) {
+            mContentViewCore.onShow();
+        } else if (!contentViewCoreVisible && mIsContentViewCoreVisible) {
+            mContentViewCore.onHide();
+        }
+        mIsContentViewCoreVisible = contentViewCoreVisible;
     }
 
     /**

android_webview/renderer/aw_content_renderer_client.cc

@@ -7,6 +7,7 @@
 #include <vector>
 
 #include "android_webview/common/aw_resource.h"
+#include "android_webview/common/aw_switches.h"
 #include "android_webview/common/render_view_messages.h"
 #include "android_webview/common/url_constants.h"
 #include "android_webview/grit/aw_resources.h"
@@ -18,6 +19,7 @@
 #include "android_webview/renderer/aw_render_frame_ext.h"
 #include "android_webview/renderer/aw_render_view_ext.h"
 #include "android_webview/renderer/print_render_frame_observer.h"
+#include "base/command_line.h"
 #include "base/i18n/rtl.h"
 #include "base/message_loop/message_loop.h"
 #include "base/strings/string_util.h"
@@ -47,8 +49,9 @@ using content::RenderThread;
 
 namespace android_webview {
 
-AwContentRendererClient::AwContentRendererClient() {
-}
+AwContentRendererClient::AwContentRendererClient()
+    : enable_page_visibility_(base::CommandLine::ForCurrentProcess()->HasSwitch(
+          switches::kEnablePageVisibility)) {}
 
 AwContentRendererClient::~AwContentRendererClient() {
 }
@@ -171,6 +174,9 @@ void AwContentRendererClient::AddKeySystems(
 bool AwContentRendererClient::ShouldOverridePageVisibilityState(
     const content::RenderFrame* render_frame,
     blink::WebPageVisibilityState* override_state) {
+  if (enable_page_visibility_)
+    return false;
+
   // webview is always visible due to rendering requirements.
   *override_state = blink::WebPageVisibilityStateVisible;
   return true;

android_webview/renderer/aw_content_renderer_client.h

@@ -44,6 +44,7 @@ class AwContentRendererClient : public content::ContentRendererClient {
  private:
   scoped_ptr<AwRenderProcessObserver> aw_render_process_observer_;
   scoped_ptr<visitedlink::VisitedLinkSlave> visited_link_slave_;
+  const bool enable_page_visibility_;
 };
 
 }  // namespace android_webview