Add an histogram to differentiate between hang types of the renderer

content/browser/renderer_host/render_widget_host_delegate.h

 // Copyright (c) 2012 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.
 
 #ifndef CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_DELEGATE_H_
 #define CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_DELEGATE_H_
 
 #include <stdint.h>
 
 #include <vector>
@@ skipping 115 matching lines @@
   // RenderWidgetHost to this function to determine who should ultimately
   // consume the event.  This facilitates keyboard event routing with
   // out-of-process iframes, where multiple RenderWidgetHosts may be involved
   // in rendering a page, yet keyboard events all arrive at the main frame's
   // RenderWidgetHostView.  When a main frame's RenderWidgetHost is passed in,
   // the function returns the focused frame that should consume keyboard
   // events. In all other cases, the function returns back |receiving_widget|.
   virtual RenderWidgetHostImpl* GetFocusedRenderWidgetHost(
       RenderWidgetHostImpl* receiving_widget);
 
+  // Enum used in histograms to differentiate between the different

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

nit: Enum is redundant, as it is obvious from the type definition below.

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

Done.

+  // types of renderer hang reported by
+  // RenderWidgetHostDelegate::RendererUnresponsive.
+  // Only add values at the end, do not delete values.

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

Does that mean we will keep this enum/UMA forever? Is it possible to use some
other mechanism which we aren't stuck with? Maybe DumpWithoutCrashing?

[Alexei Svitkine (slow), 2016/07/12 18:36:40]

You can always delete histograms. That's fine.

The point is you can't renumber an enum or re-use enum values (without at least
renaming the histogram), otherwise values will be inconsistent between versions.

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

I'm not sure how DumpWithoutCrashing works, and it's not very clear from the
description either. I need reports from the field on the distribution of the
different types of renderer hang, to see where the huge spike we're seeing is
coming from.

[nasko, 2016/07/15 17:32:08]

DumpWithoutCrashing literally does what it says - generates a crash report, as
thought we had a crash at the line we call it on, but doesn't really crash the
process itself. It is useful tool to debug issues that are hard to understand,
but it does add overhead.
Ah, good to know. Thanks!
Let's use a histogram then, as it doesn't have much overhead and we might want
to keep it for a while.

+  enum RendererUnresponsiveType {
+    RENDERER_UNRESPONSIVE_UNKNOWN = 0,
+    RENDERER_UNRESPONSIVE_IN_FLIGHT_EVENTS = 1,
+    RENDERER_UNRESPONSIVE_DIALOG_CLOSED = 2,
+    RENDERER_UNRESPONSIVE_DIALOG_SUPPRESSED = 3,
+    RENDERER_UNRESPONSIVE_BEFORE_UNLOAD = 4,
+    RENDERER_UNRESPONSIVE_UNLOAD = 5,
+    RENDERER_UNRESPONSIVE_CLOSE_PAGE = 6,
+    RENDERER_UNRESPONSIVE_MAX = RENDERER_UNRESPONSIVE_CLOSE_PAGE,
+  };
+
   // Notification that the renderer has become unresponsive. The
   // delegate can use this notification to show a warning to the user.
-  virtual void RendererUnresponsive(RenderWidgetHostImpl* render_widget_host) {}
+  virtual void RendererUnresponsive(RenderWidgetHostImpl* render_widget_host,
+                                    RendererUnresponsiveType type) {}
 
   // Notification that a previously unresponsive renderer has become
   // responsive again. The delegate can use this notification to end the
   // warning shown to the user.
   virtual void RendererResponsive(RenderWidgetHostImpl* render_widget_host) {}
 
   // Requests to lock the mouse. Once the request is approved or rejected,
   // GotResponseToLockMouseRequest() will be called on the requesting render
   // widget host.
   virtual void RequestToLockMouse(RenderWidgetHostImpl* render_widget_host,
@@ skipping 40 matching lines @@
   // Returns the TextInputManager tracking text input state.
   virtual TextInputManager* GetTextInputManager();
 
  protected:
   virtual ~RenderWidgetHostDelegate() {}
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_DELEGATE_H_