gpu: Fix some context lost marking glitches+leaks and add UMA stats

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 784843737e613e7d0e3bb02a7790819a225811fb..478de91db938cd11f8ae6507d006f8f6ad2860a7 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -11430,6 +11430,16 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   </summary>
 </histogram>
 
+<histogram name="GPU.BrowserCompositorContextLost" enum="ContextLostReason">
+  <owner>sievers@chromium.org</owner>
+  <summary>The reason a GPU command buffer context was lost.</summary>
+</histogram>
+
+<histogram name="GPU.BrowserMainThreadContextLost" enum="ContextLostReason">
+  <owner>sievers@chromium.org</owner>
+  <summary>The reason a GPU command buffer context was lost.</summary>

[Alexei Svitkine (slow), 2015/04/24 19:13:21]

Please update these descriptions to differentiate them from each other.

[no sievers, 2015/04/24 19:26:25]

Done.

+</histogram>
+
 <histogram name="GPU.CollectContextGraphicsInfo" units="microseconds">
   <owner>vangelis@chromium.org</owner>
   <summary>
@@ -11483,6 +11493,21 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   </summary>
 </histogram>
 
+<histogram name="GPU.RenderCompositorContextLost" enum="ContextLostReason">
+  <owner>sievers@chromium.org</owner>
+  <summary>The reason a GPU command buffer context was lost.</summary>
+</histogram>
+
+<histogram name="GPU.RenderMainThreadContextLost" enum="ContextLostReason">
+  <owner>sievers@chromium.org</owner>
+  <summary>The reason a GPU command buffer context was lost.</summary>
+</histogram>
+
+<histogram name="GPU.RenderWorkerContextLost" enum="ContextLostReason">
+  <owner>sievers@chromium.org</owner>
+  <summary>The reason a GPU command buffer context was lost.</summary>
+</histogram>
+
 <histogram name="GPU.TextureRG" enum="BooleanAvailable">
   <owner>reveman@chromium.org</owner>
   <summary>
@@ -11491,6 +11516,26 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   </summary>
 </histogram>
 
+<histogram name="GPU.UnknownContextTypeLost" enum="ContextLostReason">
+  <owner>sievers@chromium.org</owner>
+  <summary>The reason a GPU command buffer context was lost.</summary>
+</histogram>
+
+<histogram name="GPU.VideoAcceleratorContextLost" enum="ContextLostReason">
+  <owner>sievers@chromium.org</owner>
+  <summary>The reason a GPU command buffer context was lost.</summary>
+</histogram>
+
+<histogram name="GPU.VideoCaptureContextLost" enum="ContextLostReason">
+  <owner>sievers@chromium.org</owner>
+  <summary>The reason a GPU command buffer context was lost.</summary>
+</histogram>
+
+<histogram name="GPU.WebGLContextLost" enum="ContextLostReason">

[Alexei Svitkine (slow), 2015/04/24 19:13:21]

Have you considered formulating these histograms in a way that lets you use
histogram_suffixes feature in this file to avoid extra repetition in this file?

for example, the following naming convention would allow this:

GPU.ContextLost.VideoCapture
GPU.ContextLost.WebGL

etc.

In addition to a more concise definition in the XML file, you'll also get better
grouping on the dashboard.

[no sievers, 2015/04/24 19:26:25]

Done. Thanks, that is much better.

+  <owner>sievers@chromium.org</owner>
+  <summary>The reason a GPU command buffer context was lost.</summary>
+</histogram>
+
 <histogram name="Hardware.Display.Count.OnChange">
   <owner>erikchen@chromium.org</owner>
   <summary>
@@ -48073,6 +48118,22 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   <int value="22" label="App banner setting (Android only)"/>
 </enum>
 
+<enum name="ContextLostReason" type="int">
+  <summary>The reason for losing a GPU context.</summary>
+  <int value="0" label="CONTEXT_INIT_FAILED"/>
+  <int value="1" label="CONTEXT_LOST_GPU_CHANNEL_ERROR"/>
+  <int value="2" label="CONTEXT_PARSE_ERROR_INVALID_SIZE"/>
+  <int value="3" label="CONTEXT_PARSE_ERROR_OUT_OF_BOUNDS"/>
+  <int value="4" label="CONTEXT_PARSE_ERROR_UNKNOWN_COMMAND"/>
+  <int value="5" label="CONTEXT_PARSE_ERROR_INVALID_ARGS"/>
+  <int value="6" label="CONTEXT_PARSE_ERROR_GENERIC_ERROR"/>
+  <int value="7" label="CONTEXT_LOST_GUILTY"/>
+  <int value="8" label="CONTEXT_LOST_INNOCENT"/>
+  <int value="9" label="CONTEXT_LOST_UNKNOWN"/>
+  <int value="10" label="CONTEXT_LOST_OUT_OF_MEMORY"/>
+  <int value="11" label="CONTEXT_LOST_MAKECURRENT_FAILED"/>
+</enum>
+
 <enum name="CookieDeletionCause" type="int">
   <summary>Reason why a cookie was removed from the cookie store</summary>
   <int value="0" label="explicit">