Add shared bitmap managers for browser and renderer processes.

cc/resources/shared_bitmap.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/resources/shared_bitmap.h"
 
+#include "base/numerics/safe_math.h"
+#include "base/rand_util.h"
+
 namespace cc {
 
 SharedBitmap::SharedBitmap(
     base::SharedMemory* memory,
     const SharedBitmapId& id,
     const base::Callback<void(SharedBitmap*)>& free_callback)
     : memory_(memory), id_(id), free_callback_(free_callback) {}
 
 SharedBitmap::~SharedBitmap() { free_callback_.Run(this); }
 
+// static
+bool SharedBitmap::GetSizeInBytes(const gfx::Size& size,
+                                  size_t* size_in_bytes) {
+  base::CheckedNumeric<int> s = size.width();

[jschuh, 2014/03/10 22:18:54]

Do you still want a check that height and width are greater than zero in here
somewhere? You'll catch any overflows, but couldn't you still get a negative or
zero size?

+  s *= size.height();
+  s *= 4;
+  if (!s.IsValid())
+    return false;
+  *size_in_bytes = s.ValueOrDie();
+  return true;
+}
+
+// static
+SharedBitmapId SharedBitmap::GenerateId() {
+  SharedBitmapId id;
+  // Needs cryptographically-secure random numbers.
+  base::RandBytes(id.name, sizeof(id.name));
+  return id;
+}
+
 }  // namespace cc