mac: ensure ui::Compositor exists for visible RWHVs

content/browser/renderer_host/render_widget_host_view_mac.mm

Index: content/browser/renderer_host/render_widget_host_view_mac.mm
diff --git a/content/browser/renderer_host/render_widget_host_view_mac.mm b/content/browser/renderer_host/render_widget_host_view_mac.mm
index 6b759cee848fc22a310e525221104b0a0af13b9c..68b34768d253b8c8c3a35b4005eec4b18cae408b 100644
--- a/content/browser/renderer_host/render_widget_host_view_mac.mm
+++ b/content/browser/renderer_host/render_widget_host_view_mac.mm
@@ -597,6 +597,9 @@ RenderWidgetHostViewMac::RenderWidgetHostViewMac(RenderWidgetHost* widget,
         ->GetInputEventRouter()
         ->AddSurfaceIdNamespaceOwner(GetSurfaceIdNamespace(), this);
   }
+
+  if (!render_widget_host_->is_hidden())
+    EnsureBrowserCompositorView();
 }
 
 RenderWidgetHostViewMac::~RenderWidgetHostViewMac() {
@@ -640,6 +643,7 @@ cc::SurfaceId RenderWidgetHostViewMac::SurfaceIdForTesting() const {
 // RenderWidgetHostViewMac, RenderWidgetHostView implementation:
 
 void RenderWidgetHostViewMac::EnsureBrowserCompositorView() {
+  DCHECK(!render_widget_host_->is_hidden());
   TRACE_EVENT0("browser",
                "RenderWidgetHostViewMac::EnsureBrowserCompositorView");
 
@@ -716,6 +720,7 @@ void RenderWidgetHostViewMac::DestroySuspendedBrowserCompositorViewIfNeeded() {
 
   // This should only be reached if |render_widget_host_| is hidden, destroyed,
   // or in the process of being destroyed.
+  DCHECK(!render_widget_host_ || render_widget_host_->is_hidden());
   DestroyBrowserCompositorView();
 }
 
@@ -887,8 +892,12 @@ RenderWidgetHost* RenderWidgetHostViewMac::GetRenderWidgetHost() const {
 void RenderWidgetHostViewMac::Show() {
   ScopedCAActionDisabler disabler;
   [cocoa_view_ setHidden:NO];
-  if (!render_widget_host_->is_hidden())
+  if (!render_widget_host_->is_hidden()) {
+    DCHECK_EQ(browser_compositor_state_, BrowserCompositorActive);
     return;
+  }
+
+  WasUnOccluded();
 
   // Re-create the browser compositor. If the DelegatedFrameHost has a cached
   // frame from the last time it was visible, then it will immediately be
@@ -896,8 +905,6 @@ void RenderWidgetHostViewMac::Show() {
   // frame is swapped.
   EnsureBrowserCompositorView();
 
-  WasUnOccluded();
-
   // If there is not a frame being currently drawn, kick one, so that the below
   // pause will have a frame to wait on.
   render_widget_host_->ScheduleComposite();
@@ -917,6 +924,11 @@ void RenderWidgetHostViewMac::Hide() {
     // completes. As a result you won't get a thumbnail for the page unless you
     // execute these two statements in this specific order.
     render_widget_host_->WasHidden();
+    // Re-check hidden flag, as the thumbnail generation could have called

[enne (OOO), 2016/06/15 22:07:44]

This was the cause of the white tabs.  I added a bunch more dchecks to try to
avoid this.  Show now makes sure that if it early outs, that the browser is
already created.  Creating and destroying the browser compositor also verify
that the RWH hidden state is as expected.

This also fixes the webrtc regression.  The tab switching test was extremely
noisy when run locally but it looked slightly better with this change, so will
reland and see what the bots look like.

+    // WasUnOccluded and unhidden itself.
+    if (!render_widget_host_->is_hidden()) {
+      return;
+    }
     SuspendBrowserCompositorView();
   }
   DestroySuspendedBrowserCompositorViewIfNeeded();
@@ -932,6 +944,7 @@ void RenderWidgetHostViewMac::WasUnOccluded() {
       render_widget_host_->GetLatencyComponentId(),
       0);
   render_widget_host_->WasShown(renderer_latency_info);
+  EnsureBrowserCompositorView();
 }
 
 void RenderWidgetHostViewMac::WasOccluded() {
@@ -1494,8 +1507,7 @@ void RenderWidgetHostViewMac::OnSwapCompositorFrame(
     gfx::Size dip_size = gfx::ConvertSizeToDIP(scale_factor, pixel_size);
 
     root_layer_->SetBounds(gfx::Rect(dip_size));
-    if (!render_widget_host_->is_hidden()) {
-      EnsureBrowserCompositorView();
+    if (browser_compositor_ && browser_compositor_->compositor()) {
       browser_compositor_->compositor()->SetScaleAndSize(
           scale_factor, pixel_size);
     }