Modified GPU command signature hash to use a binary representation.

gpu/command_buffer/service/framebuffer_manager.cc

Index: gpu/command_buffer/service/framebuffer_manager.cc
diff --git a/gpu/command_buffer/service/framebuffer_manager.cc b/gpu/command_buffer/service/framebuffer_manager.cc
index 4022b3defaa1e286e85e72f7ac6aa702fa1e9fb2..95aa2f73f0a65e99513c50df0287fc3e49d1e273 100644
--- a/gpu/command_buffer/service/framebuffer_manager.cc
+++ b/gpu/command_buffer/service/framebuffer_manager.cc
@@ -508,12 +508,14 @@ GLenum Framebuffer::GetStatus(
   // Check if we have this combo already.
   std::string signature;

[vmiura, 2014/09/23 20:26:47]

I think it would help to pre-reserve enough space for a typical framebuffer e.g.
1 texture for color buffer + 2 * renderbuffers for depth & stencil.

i.e. signature.reserve(xyz);

[David Yen, 2014/09/23 20:45:24]

Since I will be adding structures for the binary blobs, I'll just implement a
function to return the size of the structures.

   if (allow_framebuffer_combo_complete_map_) {
-    signature = base::StringPrintf("|FBO|target=%04x", target);
+    signature.append("|Target|");
+    signature.append(reinterpret_cast<const char*>(&target), sizeof(target));
+    signature.push_back('|');

[vmiura, 2014/09/23 20:26:47]

I think we could remove fillers like "|Target|" and "|".

[David Yen, 2014/09/23 20:45:24]

I think it's a good idea to keep marker tags to ensure the binary data will be
unique, this can be a problem especially when having binary blobs containing
enums.

[vmiura, 2014/09/23 22:37:17]

I'd think we need to keep them in the attachments to avoid collisions, but this
"|Target|" ... "|" is a constant that I think we can remove.

[David Yen, 2014/09/23 22:42:51]

Done. Removed it in the last patch.

     for (AttachmentMap::const_iterator it = attachments_.begin();
          it != attachments_.end(); ++it) {
       Attachment* attachment = it->second.get();
-      signature +=
-          base::StringPrintf("|Attachment|attachmentpoint=%04x", it->first);
+      signature.append(reinterpret_cast<const char*>(&it->first),
+                       sizeof(it->first));
       attachment->AddToSignature(texture_manager, &signature);
     }