content: Add DeletedDiscardableSharedMemory IPC.

This provides a mechanism for child processes to notify the
browser process that a discardable memory segment has been
deleted. This reduces the chance of the browser unnecessarily
purging a memory segment that is still useful and it makes
total discardable memory usage stats in the browser process
better match current usage by all child processes.

BUG=
TEST=content_unittests --gtest_filter=DiscardableSharedMemoryHeapTest.DeletedCallback, content_browsertests --gtest_filter=ChildDiscardableSharedMemoryManagerBrowserTest.ReleaseFreeMemory

Review URL: https://codereview.chromium.org/1009203004

Cr-Commit-Position: refs/heads/master@{#320848}

1 files changed, 3 insertions, 1 deletions

diff --git a/content/child/child_discardable_shared_memory_manager.h b/content/child/child_discardable_shared_memory_manager.h
index 27c8b83..cc534e4 100644
--- a/content/child/child_discardable_shared_memory_manager.h
+++ b/content/child/child_discardable_shared_memory_manager.h
@@ -11,6 +11,7 @@
 #include "content/child/thread_safe_sender.h"
 #include "content/common/content_export.h"
 #include "content/common/discardable_shared_memory_heap.h"
+#include "content/common/host_discardable_shared_memory_manager.h"
 
 namespace content {
 
@@ -35,7 +36,8 @@ class CONTENT_EXPORT ChildDiscardableSharedMemoryManager
 
  private:
   scoped_ptr<base::DiscardableSharedMemory>
-  AllocateLockedDiscardableSharedMemory(size_t size);
+  AllocateLockedDiscardableSharedMemory(size_t size,
+                                        DiscardableSharedMemoryId id);
   void MemoryUsageChanged(size_t new_bytes_allocated,
                           size_t new_bytes_free) const;