Add UMA reporting on failure to load ppapi plugins.

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 07a530c669a85abb4195a52a5b6d3f928e083d28..7b538f9c83bfe8f0092871545b0a5b53736b1a0f 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -2600,6 +2600,14 @@ other types of suffix sets.
   </summary>
 </histogram>
 
+<histogram name="Plugin.PpapiBrokerLoadResult" enum="PluginLoadResult">
+  <summary>The result from an attempt to load a PPAPI broker.</summary>
+</histogram>
+
+<histogram name="Plugin.PpapiPluginLoadResult" enum="PluginLoadResult">
+  <summary>The result from an attempt to load a PPAPI plugin.</summary>
+</histogram>
+
 <histogram name="Prerender.FinalStatus" enum="PrerenderFinalStatus">
   <summary>
     Final status for prerender pages - either success, or why it was canceled.
@@ -4886,6 +4894,13 @@ other types of suffix sets.
   <int value="15" label="INVALID_URL"/>
 </enum>
 
+<enum name="PluginLoadResult" type="int">
+  <int value="0" label="LOAD_SUCCESS"/>
+  <int value="1" label="LOAD_FAILED"/>
+  <int value="2" label="ENTRY_POINT_MISSING"/>
+  <int value="3" label="INIT_FAILED"/>
+</enum>
+
 <enum name="PreconnectMotivation" type="int">
   <int value="0" label="MOUSE_OVER_MOTIVATED"/>
   <int value="1" label="PAGE_SCAN_MOTIVATED"/>
@@ -5397,6 +5412,17 @@ other types of suffix sets.
   <affected-histogram name="Renderer4.BeginToFinishDoc"/>
 </fieldtrial>
 
+<fieldtrial name="PpapiPluginName">
+  <group name="libpepflashplayer.so" label="Flash player on Linux or Cros"/>
+  <group name="libwidevinecdmadapter.so" label="Widevine CDM on Linux or Cros"/>
+  <group name="pepflashplayer.dll" label="Flash player on Windows"/>
+  <group name="PepperFlashPlayer.plugin" label="Flash player on Mac"/>
+  <group name="widevinecdmadapter.dll" label="Widevine CDM on Windows"/>
+  <group name="widevinecdmadapter.plugin" label="Widevine CDM on Mac"/>
+  <affected-histogram name="Plugin.PpapiBrokerLoadResult"/>
+  <affected-histogram name="Plugin.PpapiPluginLoadResult"/>
+</fieldtrial>
+
 <fieldtrial name="Prefetch">
   <group name="ContentPrefetchPrefetchOff"
       label="Prefetch is completely disabled."/>