Add retry logic to V8Initializer snapshot loading files for suspected A/V problem.

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 8d6e333b0b5a448786e2ebb6c152e9320043eab7..0a19b827bcdaaafe7a2c52f4abb3b49021b164c0 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -11407,6 +11407,18 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   <summary>Http response codes in NetworkLocationRequest.</summary>
 </histogram>
 
+<histogram name="gin.V8Initializer.LoadV8Snapshot.Result"

[Alexei Svitkine (slow), 2015/05/07 17:09:09]

This seems to be adding a new top-level prefix for histograms - is it possible
to re-use an existing prefix instead, for e.g. V8.*?

[oth, 2015/05/08 09:21:53]

Done.

+    enum="V8InitializerLoadV8SnapshotResult">
+  <owner>oth@chromium.org</owner>
+  <summary>Results from snapshot loading.</summary>
+</histogram>
+
+<histogram name="gin.V8Initializer.OpenV8File.Result"
+    enum="V8InitializerOpenV8FileResult">
+  <owner>oth@chromium.org</owner>
+  <summary>Results from opening V8 snapshot files.</summary>
+</histogram>
+
 <histogram name="GoogleNow.Card.Button.Clicked0" enum="GoogleNowCardTypeId">
   <owner>robliao@chromium.org</owner>
   <owner>skare@chromium.org</owner>
@@ -64294,6 +64306,20 @@ To add a new entry, add it with any value and run test to compute valid value.
   <int value="6" label="CHECKSUM_MISMATCH">Reject due to checksum mismatch</int>
 </enum>
 
+<enum name="V8InitializerLoadV8SnapshotResult" type="int">
+  <int value="0" label="SUCCESS">Load succeeded</int>
+  <int value="1" label="FAILED_OPEN">Failure to open snapshot file</int>
+  <int value="2" label="FAILED_MAP">Failed to map snapshot</int>
+  <int value="3" label="FAILED_VERIFY">Failed to verify snapshot</int>
+</enum>
+
+<enum name="V8InitializerOpenV8FileResult" type="int">
+  <int value="0" label="OPENED">Opened without issue</int>
+  <int value="1" label="OPENED_RETRY">Opened after one or more retries</int>
+  <int value="2" label="FAILED_IN_USE">Failed because file in use</int>
+  <int value="3" label="FAILED_OTHER">Failed for other reason</int>
+</enum>
+
 <enum name="ValidateMenuItemSelectorType" type="int">
   <int value="0"
       label="The menu items' associated action is an unknown selector."/>