content: Update crash key and discardable memory usage counter in child process.

content/common/discardable_shared_memory_heap.h

Index: content/common/discardable_shared_memory_heap.h
diff --git a/content/common/discardable_shared_memory_heap.h b/content/common/discardable_shared_memory_heap.h
index 919d4c67996b28c42ef483caa360718011698937..0c7f5a428c9b6fbba93042ea429fb8adeb2fd0e5 100644
--- a/content/common/discardable_shared_memory_heap.h
+++ b/content/common/discardable_shared_memory_heap.h
@@ -68,8 +68,9 @@ class CONTENT_EXPORT DiscardableSharedMemoryHeap {
   // memory. If found, the span is removed from the free list and returned.
   scoped_ptr<Span> SearchFreeList(size_t blocks);
 
-  // Release shared memory segments that have been purged.
-  void ReleaseFreeMemory();
+  // Release shared memory segments that have been purged. Returns bytes of
+  // memory that were released.
+  size_t ReleaseFreeMemory();
 
  private:
   scoped_ptr<Span> RemoveFromFreeList(Span* span);