viz: Fix frame eviction logic with --enable-viz.

The FrameEvictionManager expects a response from
DelegatedFrameHost::EvictDelegatedFrame() otherwise it will DCHECK and
crash. Implement the correct logic in DelegatedFrameHost. There is no
CompositorFrameSinkSupport to clear, but we clear the SurfaceLayer which
will drop the surface reference to the evicted frame.

Bug: 777881
Change-Id: Id6725d6cdb141c668b8217419535863ecf586a17
Reviewed-on: https://chromium-review.googlesource.com/829618
Commit-Queue: kylechar <kylechar@chromium.org>
Reviewed-by: Fady Samuel <fsamuel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#524717}

content/browser/renderer_host/delegated_frame_host.cc

@@ -525,7 +525,6 @@ void DelegatedFrameHost::SubmitCompositorFrame(
         local_surface_id, std::move(frame), std::move(hit_test_region_list));
     DCHECK(result);
   }
-
 }
 
 void DelegatedFrameHost::ClearDelegatedFrame() {
@@ -617,27 +616,25 @@ void DelegatedFrameHost::OnBeginFrame(const viz::BeginFrameArgs& args) {
 }
 
 void DelegatedFrameHost::EvictDelegatedFrame() {
-  if (enable_viz_) {
-    NOTIMPLEMENTED();
-    return;
-  }
-
   if (!HasFallbackSurface())
     return;
 
   if (enable_surface_synchronization_) {
     client_->DelegatedFrameHostGetLayer()->SetFallbackSurfaceId(
         viz::SurfaceId());
-    support_->EvictCurrentSurface();
-    frame_evictor_->DiscardedFrame();
-    return;
+  } else {
+    client_->DelegatedFrameHostGetLayer()->SetShowSolidColorContent();
+    resize_lock_.reset();
+    UpdateGutters();
   }
 
-  client_->DelegatedFrameHostGetLayer()->SetShowSolidColorContent();
-  support_->EvictCurrentSurface();
-  resize_lock_.reset();
+  // TODO(samans): Ensure that with --enable-viz the latest frame is evicted and
+  // that DelegatedFrameHost updates the SurfaceLayer when the frame becomes
+  // visible again.
+  if (!enable_viz_)
+    support_->EvictCurrentSurface();
+
   frame_evictor_->DiscardedFrame();
-  UpdateGutters();
 }
 
 // static