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..eb97ebf19ba17c8a5413111fb45b6c0343be0e6e 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 hang_monitor_reason);
 
   // 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_ has been started. Used to
+  // report histograms if the renderer is hung.
+  RenderWidgetHostDelegate::RendererUnresponsiveType hang_monitor_reason_;
+
   // 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_;