Add shared bitmap managers for browser and renderer processes.

cc/resources/shared_bitmap.h

Index: cc/resources/shared_bitmap.h
diff --git a/cc/resources/shared_bitmap.h b/cc/resources/shared_bitmap.h
index 9575068411ac512038088663b7854aba5b9ada00..2382098b95043e16f76cedf71da573c7cb3f5f68 100644
--- a/cc/resources/shared_bitmap.h
+++ b/cc/resources/shared_bitmap.h
@@ -10,6 +10,7 @@
 #include "base/memory/shared_memory.h"
 #include "cc/base/cc_export.h"
 #include "gpu/command_buffer/common/mailbox.h"
+#include "ui/gfx/size.h"
 
 namespace base { class SharedMemory; }
 
@@ -38,6 +39,10 @@ class CC_EXPORT SharedBitmap {
 
   SharedBitmapId id() { return id_; }
 
+  static size_t GetSizeInBytes(const gfx::Size& size);
+
+  static SharedBitmapId GenerateId();
+
  private:
   base::SharedMemory* memory_;
   SharedBitmapId id_;