Expand UMA coverage for compositor-handled events and fling FPS

tools/metrics/histograms/histograms.xml

Index: tools/metrics/histograms/histograms.xml
diff --git a/tools/metrics/histograms/histograms.xml b/tools/metrics/histograms/histograms.xml
index 156913886691d88317b39ac951ec44852e954e9e..c22e75bb251bcb2b625da856a952291c9a47dc9e 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -6701,6 +6701,22 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   </summary>
 </histogram>
 
+<histogram name="Event.Frequency.Renderer.FlingAnimate" units="hertz">
+  <owner>rbyers@chromium.org</owner>
+  <summary>
+    Average animation frequency of a main-thread fling instance over its

[Mark P, 2014/12/01 21:27:36]

A histogram description should say when an entry is emitted.

If indeed this histogram emits something that's an average of something else,
the description needs to clearly state how it decides how many items to average
/ over what period.  In this case, I think you need to describe how a lifetime
is determined.

It would also be nice if the description mentioned renderer, rather than merely
finding it in the histogram name.

Finally, I vaguely recall that sometimes renderers are killed (in order to be
shut down faster) rather than going through the normal close process.  Make sure
your answer to the "when is this emitted" either implicitly or explicitly says
whether this will be emitted under those conditions.

ditto  below

[jdduke (slow), 2014/12/01 22:47:30]

Done.
Done.
Done.

+    lifetime.
+  </summary>
+</histogram>
+
+<histogram name="Event.Frequency.RendererImpl.FlingAnimate" units="hertz">
+  <owner>rbyers@chromium.org</owner>
+  <summary>
+    Average animation frequency of an impl-thread fling instance over its
+    lifetime.
+  </summary>
+</histogram>
+
 <histogram name="Event.GestureCreated" enum="UIEventType">
   <owner>kuscher@google.com</owner>
   <owner>rbyers@chromium.org</owner>
@@ -7045,14 +7061,15 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   </summary>
 </histogram>
 
-<histogram name="Event.Latency.RendererImpl.GestureScroll" units="microseconds">

[Mark P, 2014/12/01 21:27:36]

Please keep this old histogram name + description + obsolete message, even
though you're adding a new histogram that is a .Something extension of it.

[jdduke (slow), 2014/12/01 22:47:30]

Done.

-  <obsolete>
-    Deprecated 12/2013 and replaced by Event.Latency.RendererImpl.GestureScroll2
-  </obsolete>
+<histogram name="Event.Latency.RendererImpl" units="microseconds">
   <owner>rbyers@chromium.org</owner>
   <summary>
-    Time between initial creation of touch event and when the resulting
-    ScrollGesture reaches Impl thread. Maximum is 200ms.
+    Time between input event creation and the renderer impl thread receiving and
+    starting to process the event. For touch events on Windows, we measure from
+    when the event reaches Chrome, whereas on other platforms we use the

[Mark P, 2014/12/01 21:27:36]

to be clear:
other platforms includes (iOS, Android, Mac, Linux, and ChromeOS)
i.e., all those platforms include events with a timestamp you get from the
kernel?

[jdduke (slow), 2014/12/01 22:47:30]

Yes.

+    timestamp from the kernel. On Windows, this metric is only reported when
+    |IsHighResNowFastAndReliable| is true, which will introduce some sampling
+    bias.
   </summary>
 </histogram>
 
@@ -7065,7 +7082,7 @@ Therefore, the affected-histogram name has to have at least one dot in it.
     the touch event reaches Chrome, whereas on other platforms we use the
     timestamp from the kernel. On Windows, this metric is only reported when
     |IsHighResNowFastAndReliable| is true, which will introduce some sampling
-    bias. This supersedes the Event.Latency.RendererImpl.GestureScroll metric.
+    bias.
   </summary>
 </histogram>
 
@@ -60545,6 +60562,7 @@ To add a new entry, add it with any value and run test to compute valid value.
   <suffix name="Undefined" label="For unknown or undefined events."/>
   <affected-histogram name="Event.Latency.Renderer"/>
   <affected-histogram name="Event.Latency.Renderer2"/>
+  <affected-histogram name="Event.Latency.RendererImpl"/>
 </histogram_suffixes>
 
 <histogram_suffixes name="ResourcePrefetchPredictorNetworkTypePrefetch"