Revert of Set crash key if WM_QUIT message is received on GPU message loop....

Revert of Set crash key if WM_QUIT message is received on GPU message loop. (patchset #2 id:20001 of https://codereview.chromium.org/2342713002/ )

Reason for revert:
Forgot key registration.

Original issue's description:
> Set crash key if WM_QUIT message is received on GPU message loop.
>
> Threads seem to be exiting unexpectedly, so to help debugging set a
> crash key if an unexpected WM_QUIT message is received.
>
> BUG=647068
>
> Committed: https://crrev.com/fafd9b39256b14f96283e5155d05e7f8f805689c
> Cr-Commit-Position: refs/heads/master@{#418753}

TBR=dcheng@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=647068

Review-Url: https://codereview.chromium.org/2339123003
Cr-Commit-Position: refs/heads/master@{#418790}

base/message_loop/message_pump_win.cc

@@ -9,7 +9,6 @@
 
 #include <limits>
 
-#include "base/debug/crash_logging.h"
 #include "base/memory/ptr_util.h"
 #include "base/message_loop/message_loop.h"
 #include "base/metrics/histogram.h"
@@ -637,11 +636,6 @@ bool MessagePumpForGpu::ProcessNextMessage() {
     return false;
 
   if (msg.message == WM_QUIT) {
-    // Try to figure out if we've received a WM_QUIT targeted towards a
-    // window. http://crbug.com/647068
-    // TODO(jbauman): Remove once we've got some data about this.
-    base::debug::SetCrashKeyValue("received_quit_message",
-                                  base::StringPrintf("%d", !!msg.hwnd));
     // Repost the QUIT message so that it will be retrieved by the primary
     // GetMessage() loop.
     state_->should_quit = true;