Add an histogram to differentiate between hang types of the renderer

content/browser/renderer_host/render_widget_host_impl.h

Index: content/browser/renderer_host/render_widget_host_impl.h
diff --git a/content/browser/renderer_host/render_widget_host_impl.h b/content/browser/renderer_host/render_widget_host_impl.h
index 68fb6a44997e94f2d821458a3bd1daae81a876d5..0340dd043cb72b21a73fe68f8b950899f8099130 100644
--- a/content/browser/renderer_host/render_widget_host_impl.h
+++ b/content/browser/renderer_host/render_widget_host_impl.h
@@ -31,6 +31,7 @@
 #include "content/browser/renderer_host/input/render_widget_host_latency_tracker.h"
 #include "content/browser/renderer_host/input/synthetic_gesture.h"
 #include "content/browser/renderer_host/input/touch_emulator_client.h"
+#include "content/browser/renderer_host/render_widget_host_delegate.h"
 #include "content/browser/renderer_host/render_widget_host_view_base.h"
 #include "content/common/input/input_event_ack_state.h"
 #include "content/common/input/synthetic_gesture_packet.h"
@@ -83,7 +84,6 @@ namespace content {
 class BrowserAccessibilityManager;
 class InputRouter;
 class MockRenderWidgetHost;
-class RenderWidgetHostDelegate;
 class RenderWidgetHostOwnerDelegate;
 class SyntheticGestureController;
 class TimeoutMonitor;
@@ -287,7 +287,9 @@ class CONTENT_EXPORT RenderWidgetHostImpl : public RenderWidgetHost,
   // Starts a hang monitor timeout. If there's already a hang monitor timeout
   // the new one will only fire if it has a shorter delay than the time
   // left on the existing timeouts.
-  void StartHangMonitorTimeout(base::TimeDelta delay);
+  void StartHangMonitorTimeout(
+      base::TimeDelta delay,
+      RenderWidgetHostDelegate::RendererUnresponsiveType type);

[nasko, 2016/07/12 17:18:02]

Shouldn't this be the hang monitor reason or type? Unresponsive is a state that
is gotten into later on, not at the start of the monitor.

[clamy, 2016/07/13 10:02:22]

Done.

 
   // Stops all existing hang monitor timeouts and assumes the renderer is
   // responsive.
@@ -817,6 +819,10 @@ class CONTENT_EXPORT RenderWidgetHostImpl : public RenderWidgetHost,
   // This value indicates how long to wait before we consider a renderer hung.
   base::TimeDelta hung_renderer_delay_;
 
+  // Stores the reason the hang_monitor_timeout_ i sbeing used, to report

[nasko, 2016/07/12 17:18:03]

nit: "is being" or "has been started. Used to ..."

[clamy, 2016/07/13 10:02:21]

Done.

+  // histograms if the renderer is hung.
+  RenderWidgetHostDelegate::RendererUnresponsiveType hang_type_;

[nasko, 2016/07/12 17:18:02]

nit: hang_monitor_type_ or hang_monitor_reason_?

[clamy, 2016/07/13 10:02:22]

Done.

+
   // This value indicates how long to wait for a new compositor frame from a
   // renderer process before clearing any previously displayed content.
   base::TimeDelta new_content_rendering_delay_;