Add mechanism to signal DelegatedFrameHost that a surface is about to draw.

This allows the FrameSubscriber to request a copy of the output even when the renderer it's subscribing to hasn't changed its contents, but a child renderer (oopif or webview) has.

BUG=529378
CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel

Review URL: https://codereview.chromium.org/1365793002

Cr-Commit-Position: refs/heads/master@{#354390}

1 files changed, 15 insertions, 4 deletions

diff --git a/cc/surfaces/surface.cc b/cc/surfaces/surface.cc
index 16987cb..e3b0f5e 100644
--- a/cc/surfaces/surface.cc
+++ b/cc/surfaces/surface.cc
@@ -98,11 +98,22 @@ void Surface::QueueFrame(scoped_ptr<CompositorFrame> frame,
 
 void Surface::RequestCopyOfOutput(scoped_ptr<CopyOutputRequest> copy_request) {
   if (current_frame_ &&
-      !current_frame_->delegated_frame_data->render_pass_list.empty())
-    current_frame_->delegated_frame_data->render_pass_list.back()
-        ->copy_requests.push_back(copy_request.Pass());
-  else
+      !current_frame_->delegated_frame_data->render_pass_list.empty()) {
+    ScopedPtrVector<CopyOutputRequest>& copy_requests =
+        current_frame_->delegated_frame_data->render_pass_list.back()
+            ->copy_requests;
+
+    if (void* source = copy_request->source()) {
+      // Remove existing CopyOutputRequests made on the Surface by the same
+      // source.
+      auto to_remove = copy_requests.remove_if([source](
+          const CopyOutputRequest* x) { return x->source() == source; });
+      copy_requests.erase(to_remove, copy_requests.end());
+    }
+    copy_requests.push_back(copy_request.Pass());
+  } else {
     copy_request->SendEmptyResult();
+  }
 }
 
 void Surface::TakeCopyOutputRequests(