[DevTools] Force page redraw when enabling screencast.

When attaching to a static page, it may not produce new frames, thus
rendering screencast useless. Forcing a frame helps in this case.

BUG=none

Review URL: https://codereview.chromium.org/441623004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@287421 0039d316-1c4b-4281-b951-d872f2087c98

content/browser/devtools/renderer_overrides_handler.cc

@@ -90,6 +90,7 @@ void ParseGenericInputParams(base::DictionaryValue* params,
 
 RendererOverridesHandler::RendererOverridesHandler(DevToolsAgentHost* agent)
     : agent_(agent),
+      has_last_compositor_frame_metadata_(false),
       capture_retry_count_(0),
       weak_factory_(this) {
   RegisterCommandHandler(
@@ -191,6 +192,7 @@ void RendererOverridesHandler::OnClientDetached() {
 void RendererOverridesHandler::OnSwapCompositorFrame(
     const cc::CompositorFrameMetadata& frame_metadata) {
   last_compositor_frame_metadata_ = frame_metadata;
+  has_last_compositor_frame_metadata_ = true;
 
   if (screencast_command_)
     InnerSwapCompositorFrame();
@@ -541,8 +543,12 @@ RendererOverridesHandler::PageStartScreencast(
   host->SetTouchEventEmulationEnabled(true, true);
   bool visible = !host->is_hidden();
   NotifyScreencastVisibility(visible);
-  if (visible)
-    InnerSwapCompositorFrame();
+  if (visible) {
+    if (has_last_compositor_frame_metadata_)
+      InnerSwapCompositorFrame();
+    else
+      host->Send(new ViewMsg_ForceRedraw(host->GetRoutingID(), 0));
+  }
   return command->SuccessResponse(NULL);
 }
 

content/browser/devtools/renderer_overrides_handler.h

@@ -109,6 +109,7 @@ class CONTENT_EXPORT RendererOverridesHandler
 
   DevToolsAgentHost* agent_;
   scoped_refptr<DevToolsProtocol::Command> screencast_command_;
+  bool has_last_compositor_frame_metadata_;
   cc::CompositorFrameMetadata last_compositor_frame_metadata_;
   base::TimeTicks last_frame_time_;
   int capture_retry_count_;

content/browser/renderer_host/render_widget_host_impl.cc

@@ -186,7 +186,7 @@ RenderWidgetHostImpl::RenderWidgetHostImpl(RenderWidgetHostDelegate* delegate,
       has_touch_handler_(false),
       weak_factory_(this),
       last_input_number_(static_cast<int64>(GetProcess()->GetID()) << 32),
-      next_browser_snapshot_id_(0) {
+      next_browser_snapshot_id_(1) {
   CHECK(delegate_);
   if (routing_id_ == MSG_ROUTING_NONE) {
     routing_id_ = process_->GetNextRoutingID();

content/common/view_messages.h

@@ -977,6 +977,8 @@ IPC_MESSAGE_ROUTED2(ViewMsg_ReclaimCompositorResources,
 IPC_MESSAGE_ROUTED0(ViewMsg_SelectWordAroundCaret)
 
 // Sent by the browser to ask the renderer to redraw.
+// If |request_id| is not zero, it is added to the forced frame's latency info
+// as ui::WINDOW_SNAPSHOT_FRAME_NUMBER_COMPONENT.
 IPC_MESSAGE_ROUTED1(ViewMsg_ForceRedraw,
                     int /* request_id */)
 

content/renderer/render_view_impl.cc

@@ -1633,9 +1633,11 @@ void RenderViewImpl::GetWindowSnapshot(const WindowSnapshotCallback& callback) {
 
 void RenderViewImpl::OnForceRedraw(int id) {
   ui::LatencyInfo latency_info;
-  latency_info.AddLatencyNumber(ui::WINDOW_SNAPSHOT_FRAME_NUMBER_COMPONENT,
-                                0,
-                                id);
+  if (id) {
+    latency_info.AddLatencyNumber(ui::WINDOW_SNAPSHOT_FRAME_NUMBER_COMPONENT,
+                                  0,
+                                  id);
+  }
   scoped_ptr<cc::SwapPromiseMonitor> latency_info_swap_promise_monitor;
   if (RenderWidgetCompositor* rwc = compositor()) {
     latency_info_swap_promise_monitor =