Workaround for a crashing appcache bug seen on the crash servers

webkit/appcache/appcache_histograms.h

Index: webkit/appcache/appcache_histograms.h
===================================================================
--- webkit/appcache/appcache_histograms.h	(revision 134562)
+++ webkit/appcache/appcache_histograms.h	(working copy)
@@ -34,6 +34,15 @@
   static void AddCompletionQueueTimeSample(const base::TimeDelta& duration);
   static void AddCompletionRunTimeSample(const base::TimeDelta& duration);
 
+  static void AddMissingManifestEntrySample();
+
+  enum MissingManifestCallsiteType {
+    CALLSITE_0, CALLSITE_1, CALLSITE_2, CALLSITE_3,
+    NUM_MISSING_MANIFEST_CALLSITE_TYPES
+  };
+  static void AddMissingManifestDetectedAtCallsite(
+      MissingManifestCallsiteType type);
+
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(AppCacheHistograms);
 };