Allow ui::Compositor to disable commits during tab-switch

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 7f3cb354dc05c946fc6ce1534b5eb6a1ebcd1fea..af770742e77a00eb78df7cd135afad3fc0bc4dee 100644
--- a/content/browser/renderer_host/render_widget_host_view_mac.mm
+++ b/content/browser/renderer_host/render_widget_host_view_mac.mm
@@ -615,6 +615,7 @@ void RenderWidgetHostViewMac::EnsureBrowserCompositorView() {
   if (browser_compositor_state_ == BrowserCompositorSuspended) {
     delegated_frame_host_->SetCompositor(browser_compositor_->compositor());
     delegated_frame_host_->WasShown(ui::LatencyInfo());
+    browser_compositor_->compositor()->SetDeferCommits(false);
     browser_compositor_state_ = BrowserCompositorActive;
   }
 }
@@ -625,6 +626,10 @@ void RenderWidgetHostViewMac::SuspendBrowserCompositorView() {
 
   // Hide the DelegatedFrameHost to transition from Active -> Suspended.
   if (browser_compositor_state_ == BrowserCompositorActive) {
+    // Ensure that any changes made to the ui::Compositor do not result in new
+    // frames being produced. Note that this does not ensure that
+    // already-in-flight frames will be aborted.
+    browser_compositor_->compositor()->SetDeferCommits(true);
     // Marking the DelegatedFrameHost as removed from the window hierarchy is
     // necessary to remove all connections to its old ui::Compositor.
     delegated_frame_host_->WasHidden();