MouseMove when the mouse is down to signal compositor priority

content/renderer/scheduler/renderer_scheduler_impl.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/renderer/scheduler/renderer_scheduler_impl.h"
 
 #include "base/bind.h"
 #include "base/message_loop/message_loop_proxy.h"
 #include "base/trace_event/trace_event.h"
 #include "base/trace_event/trace_event_argument.h"
@@ skipping 102 matching lines @@
   base::TimeTicks now(Now());
   if (now < estimated_next_frame_begin_) {
     StartIdlePeriod();
     control_task_runner_->PostDelayedTask(FROM_HERE,
                                           end_idle_period_closure_.callback(),
                                           estimated_next_frame_begin_ - now);
   }
 }
 
 void RendererSchedulerImpl::DidReceiveInputEventOnCompositorThread(
-    blink::WebInputEvent::Type type) {
+    const blink::WebInputEvent& web_input_event) {
   TRACE_EVENT0(TRACE_DISABLED_BY_DEFAULT("renderer.scheduler"),
                "RendererSchedulerImpl::DidReceiveInputEventOnCompositorThread");
-  // Ignore mouse events because on windows these can very frequent.
+  // We regard MouseMove events with the left mouse button down as a signsal
+  // that the user is doing something requiring a smooth frame rate.
+  if (web_input_event.type == blink::WebInputEvent::MouseMove &&
+      web_input_event.modifiers & blink::WebInputEvent::LeftButtonDown) {

[picksi, 2015/02/06 09:23:47]

nit: Should we add blink::WebInputEvent::isLeftMouseButton(web_input_event) to
hide the implementation details and to stylistically match the calls to
blink::WebInputEvent::isMouseEventType(web_input_event.type) later on?

If you think that is too heavy handed, it might add to readability to bracket
the bitwise & parameters, as at first glance it looked to me like there were 3
checks in this if.

[alex clarke (OOO till 29th), 2015/02/06 10:12:21]

I can't change WebInputEvent in this patch since that's in the blink repository.
 I've added some brackets instead.

+    UpdateForInputEvent();
+    return;
+  }
+  // Ignore all other mouse events becuase they probably don't signal user
+  // interaction needing a smooth framerate. NOTE isMouseEventType returns false
+  // for mouse wheel events, hence we regard them as user input.
   // Ignore keyboard events because it doesn't really make sense to enter
   // compositor priority for them.
-  if (blink::WebInputEvent::isMouseEventType(type) ||
-      blink::WebInputEvent::isKeyboardEventType(type)) {
+  if (blink::WebInputEvent::isMouseEventType(web_input_event.type) ||
+      blink::WebInputEvent::isKeyboardEventType(web_input_event.type)) {
     return;
   }
   UpdateForInputEvent();
 }
 
 void RendererSchedulerImpl::DidAnimateForInputOnCompositorThread() {
   UpdateForInputEvent();
 }
 
 void RendererSchedulerImpl::UpdateForInputEvent() {
@@ skipping 203 matching lines @@
   state->SetDouble("last_input_time",
                    (last_input_time_ - base::TimeTicks()).InMillisecondsF());
   state->SetDouble(
       "estimated_next_frame_begin",
       (estimated_next_frame_begin_ - base::TimeTicks()).InMillisecondsF());
 
   return state;
 }
 
 }  // namespace content