Stop using HMAC for gpu mailboxes

For a long time, we've been using HMAC to sign the mailbox names on the GPU
process. However, we don't actually need the mailbox names to be guaranteed to
be generated by the GPU process, we only need to ensure they're unguessable.

The HMAC signature and verification has several costs:
- the cost to sign the mailbox
- the cost to verify the mailbox
- the initialization cost (e.g. starting NSS in the GPU process)

We can actually save all that cost, by just making the mailbox names
(crypto-)random.

BUG=311259

Review URL: https://codereview.chromium.org/157243002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@249922 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 4 insertions, 3 deletions

diff --git a/content/common/gpu/gpu_command_buffer_stub.cc b/content/common/gpu/gpu_command_buffer_stub.cc
index ad048c6..13b7b22 100644
--- a/content/common/gpu/gpu_command_buffer_stub.cc
+++ b/content/common/gpu/gpu_command_buffer_stub.cc
@@ -608,11 +608,12 @@ void GpuCommandBufferStub::OnSetGetBuffer(int32 shm_id,
 
 void GpuCommandBufferStub::OnProduceFrontBuffer(const gpu::Mailbox& mailbox) {
   TRACE_EVENT0("gpu", "GpuCommandBufferStub::OnProduceFrontBuffer");
-  if (!decoder_)
+  if (!decoder_) {
     LOG(ERROR) << "Can't produce front buffer before initialization.";
+    return;
+  }
 
-  if (!decoder_->ProduceFrontBuffer(mailbox))
-    LOG(ERROR) << "Failed to produce front buffer.";
+  decoder_->ProduceFrontBuffer(mailbox);
 }
 
 void GpuCommandBufferStub::OnGetState(IPC::Message* reply_message) {