Set shared memory for smoothness inside blink.

Move the allocation of the shared memory segment for ukm smoothness
from RenderWidget to LocalFrameClientImpl.

BUG=1097816

Change-Id: Ib95690ed560e80a4bd43da5be534ae82a5370fce
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2495612
Commit-Queue: Dave Tapuska <dtapuska@chromium.org>
Reviewed-by: danakj <danakj@chromium.org>
Cr-Commit-Position: refs/heads/master@{#821417}

content/renderer/render_frame_impl.h

@@ -731,9 +731,8 @@ class CONTENT_EXPORT RenderFrameImpl
   void DidCommitAndDrawCompositorFrame() override;
   void WasHidden() override;
   void WasShown() override;
-
   void SetUpSharedMemoryForSmoothness(
-      base::ReadOnlySharedMemoryRegion shared_memory);
+      base::ReadOnlySharedMemoryRegion shared_memory) override;
 
   // Binds to the fullscreen service in the browser.
   void BindFullscreen(

content/renderer/render_widget.cc

@@ -309,14 +309,6 @@ void RenderWidget::DidNavigate(ukm::SourceId source_id, const GURL& url) {
   // compositor. Note that the metrics for all frames are keyed to the main
   // frame's URL.
   layer_tree_host_->SetSourceURL(source_id, url);
-
-  DCHECK(for_frame());
-  RenderFrameImpl* render_frame =
-      RenderFrameImpl::FromWebFrame(GetFrameWidget()->LocalRoot());
-  auto shmem = layer_tree_host_->CreateSharedMemoryForSmoothnessUkm();
-  if (shmem.IsValid()) {
-    render_frame->SetUpSharedMemoryForSmoothness(std::move(shmem));
-  }
 }
 
 }  // namespace content

third_party/blink/public/web/web_local_frame_client.h

@@ -706,6 +706,11 @@ class BLINK_EXPORT WebLocalFrameClient {
 
   // Inform the widget that it was shown.
   virtual void WasShown() {}
+
+  // Called after a navigation which set the shared memory region for
+  // tracking smoothness via UKM.
+  virtual void SetUpSharedMemoryForSmoothness(
+      base::ReadOnlySharedMemoryRegion shared_memory) {}
 };
 
 }  // namespace blink

third_party/blink/renderer/core/frame/local_frame_client_impl.cc

@@ -538,6 +538,19 @@ void LocalFrameClientImpl::DispatchDidCommitLoad(
       ResetWheelAndTouchEventHandlerProperties(*web_frame_->GetFrame());
 
       web_frame_->FrameWidgetImpl()->DidNavigate();
+
+      // UKM metrics are only collected for the main frame. Ensure after
+      // a navigation on the main frame we setup the appropriate structures.
+      if (web_frame_->GetFrame()->IsMainFrame() &&
+          web_frame_->ViewImpl()->does_composite()) {
+        cc::LayerTreeHost* layer_tree_host =
+            web_frame_->FrameWidgetImpl()->LayerTreeHost();
+        auto shmem = layer_tree_host->CreateSharedMemoryForSmoothnessUkm();
+        if (shmem.IsValid()) {
+          web_frame_->Client()->SetUpSharedMemoryForSmoothness(
+              std::move(shmem));
+        }
+      }
     }
   }
   if (WebDevToolsAgentImpl* dev_tools = DevToolsAgent())