Add shared bitmap managers for browser and renderer processes.

cc/resources/shared_bitmap.cc

Index: cc/resources/shared_bitmap.cc
diff --git a/cc/resources/shared_bitmap.cc b/cc/resources/shared_bitmap.cc
index 3a6fc3589e3a8471b9a4d10e75278c76bfbe0a41..c06561447577e6961f1996c8947afe33a9f6f7b5 100644
--- a/cc/resources/shared_bitmap.cc
+++ b/cc/resources/shared_bitmap.cc
@@ -4,6 +4,9 @@
 
 #include "cc/resources/shared_bitmap.h"
 
+#include "base/numerics/safe_math.h"
+#include "base/rand_util.h"
+
 namespace cc {
 
 SharedBitmap::SharedBitmap(
@@ -14,4 +17,24 @@ SharedBitmap::SharedBitmap(
 
 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