content: Only drop fallback if sized changed while hidden

Instead of dropping fallback every time a tab goes hidden, only drop
fallback if size changes when the tab was hidden.

Bug: 822442
Change-Id: Ib1ac403f9c76cbb406ca5f85d47f6b789ca9b055
Reviewed-on: https://chromium-review.googlesource.com/965016Reviewed-by: Fady Samuel <fsamuel@chromium.org>
Commit-Queue: Saman Sami <samans@chromium.org>
Cr-Commit-Position: refs/heads/master@{#543830}

content/browser/renderer_host/delegated_frame_host.cc

@@ -267,10 +267,18 @@ void DelegatedFrameHost::WasResized(
 
   if (enable_surface_synchronization_) {
     if (!client_->DelegatedFrameHostIsVisible()) {
-      if (HasFallbackSurface()) {
+      // If the tab is resized while hidden, reset the fallback so that the next
+      // time user switches back to it the page is blank. This is preferred to
+      // showing contents of old size. Don't call EvictDelegatedFrame to avoid
+      // races when dragging tabs across displays. See https://crbug.com/813157.
+      if (pending_surface_dip_size_ != current_frame_size_in_dip_ &&
+          HasFallbackSurface()) {
         client_->DelegatedFrameHostGetLayer()->SetFallbackSurfaceId(
             viz::SurfaceId());
       }
+      // Don't update the SurfaceLayer when invisible to avoid blocking on
+      // renderers that do not submit CompositorFrames. Next time the renderer
+      // is visible, WasResized will be called again. See WasShown.
       return;
     }
 

content/browser/renderer_host/render_widget_host_view_aura.h

@@ -405,6 +405,10 @@ class CONTENT_EXPORT RenderWidgetHostViewAura
                            DeviceScaleFactorChanges);
   FRIEND_TEST_ALL_PREFIXES(RenderWidgetHostViewAuraSurfaceSynchronizationTest,
                            HideThenShow);
+  FRIEND_TEST_ALL_PREFIXES(RenderWidgetHostViewAuraSurfaceSynchronizationTest,
+                           DropFallbackIfResizedWhileHidden);
+  FRIEND_TEST_ALL_PREFIXES(RenderWidgetHostViewAuraSurfaceSynchronizationTest,
+                           DontDropFallbackIfNotResizedWhileHidden);
   FRIEND_TEST_ALL_PREFIXES(SitePerProcessHitTestBrowserTest, PopupMenuTest);
   FRIEND_TEST_ALL_PREFIXES(RenderWidgetHostViewAuraSurfaceSynchronizationTest,
                            NewContentRenderingTimeout);

content/browser/renderer_host/render_widget_host_view_aura_unittest.cc

@@ -6003,6 +6003,43 @@ TEST_F(RenderWidgetHostViewAuraSurfaceSynchronizationTest,
   EXPECT_NE(id1, id2);
 }
 
+// If a tab was resized while it's hidden, drop the fallback so next time it's
+// visible we show blank.
+TEST_F(RenderWidgetHostViewAuraSurfaceSynchronizationTest,
+       DropFallbackIfResizedWhileHidden) {
+  view_->InitAsChild(nullptr);
+  aura::client::ParentWindowWithContext(
+      view_->GetNativeView(), parent_view_->GetNativeView()->GetRootWindow(),
+      gfx::Rect());
+  view_->Show();
+  viz::LocalSurfaceId id1 = view_->GetLocalSurfaceId();
+  view_->delegated_frame_host_->OnFirstSurfaceActivation(viz::SurfaceInfo(
+      viz::SurfaceId(view_->GetFrameSinkId(), id1), 1, gfx::Size(20, 20)));
+  EXPECT_TRUE(view_->window_->layer()->GetFallbackSurfaceId()->is_valid());
+  view_->Hide();
+  view_->SetSize(gfx::Size(54, 32));
+  view_->Show();
+  EXPECT_FALSE(view_->window_->layer()->GetFallbackSurfaceId()->is_valid());
+}
+
+// If a tab is hidden and shown without being resized in the meantime, the
+// fallback SurfaceId has to be preserved.
+TEST_F(RenderWidgetHostViewAuraSurfaceSynchronizationTest,
+       DontDropFallbackIfNotResizedWhileHidden) {
+  view_->InitAsChild(nullptr);
+  aura::client::ParentWindowWithContext(
+      view_->GetNativeView(), parent_view_->GetNativeView()->GetRootWindow(),
+      gfx::Rect());
+  view_->Show();
+  viz::LocalSurfaceId id1 = view_->GetLocalSurfaceId();
+  view_->delegated_frame_host_->OnFirstSurfaceActivation(viz::SurfaceInfo(
+      viz::SurfaceId(view_->GetFrameSinkId(), id1), 1, gfx::Size(20, 20)));
+  EXPECT_TRUE(view_->window_->layer()->GetFallbackSurfaceId()->is_valid());
+  view_->Hide();
+  view_->Show();
+  EXPECT_TRUE(view_->window_->layer()->GetFallbackSurfaceId()->is_valid());
+}
+
 // This class provides functionality to test a RenderWidgetHostViewAura
 // instance which has been hooked up to a test RenderViewHost instance and
 // a WebContents instance.