Allow WebExternalTextureLayers to receive a bitmap along with a mailbox

cc/resources/texture_mailbox.cc

Index: cc/resources/texture_mailbox.cc
diff --git a/cc/resources/texture_mailbox.cc b/cc/resources/texture_mailbox.cc
index 0d4787438f46b2d5a00488d74087cc42952c79f1..273f55ebc8141cb9c114d64a9acddf790723999d 100644
--- a/cc/resources/texture_mailbox.cc
+++ b/cc/resources/texture_mailbox.cc
@@ -76,6 +76,17 @@ TextureMailbox::TextureMailbox(
       shared_memory_size_(size) {
 }
 
+TextureMailbox::TextureMailbox(
+    SkBitmap bitmap,
+    gfx::Size size,
+    const ReleaseCallback& callback)
+    : callback_(callback),
+      target_(GL_TEXTURE_2D),
+      sync_point_(0),
+      bitmap_(bitmap),
+      shared_memory_size_(size) {
+}
+
 TextureMailbox::~TextureMailbox() {
 }
 
@@ -84,6 +95,8 @@ bool TextureMailbox::Equals(const TextureMailbox& other) const {
     return ContainsMailbox(other.name());
   else if (other.IsSharedMemory())
     return ContainsHandle(other.shared_memory_->handle());
+  else if (other.IsBitmap())
+    return other.bitmap_.getPixels() == bitmap_.getPixels();
 
   DCHECK(!other.IsValid());
   return !IsValid();