Don't fetch histograms from the same process.

content/browser/gpu/gpu_process_host.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/gpu/gpu_process_host.h"
 
 #include "base/base64.h"
 #include "base/base_switches.h"
 #include "base/basictypes.h"
 #include "base/bind.h"
@@ skipping 330 matching lines @@
   // GpuProcessHostUIShim will be destroyed if either the browser exits,
   // in which case it calls GpuProcessHostUIShim::DestroyAll, or the
   // GpuProcessHost is destroyed, which happens when the corresponding GPU
   // process terminates or fails to launch.
   BrowserThread::PostTask(
       BrowserThread::UI,
       FROM_HERE,
       base::Bind(base::IgnoreResult(&GpuProcessHostUIShim::Create), host_id));
 
   process_.reset(new BrowserChildProcessHostImpl(PROCESS_TYPE_GPU, this));
+  if (in_process_)
+    process_->SetHandle(base::GetCurrentProcessHandle());

[piman, 2014/06/11 19:46:35]

Seems iffy... It will have side effects in other places (e.g.
OnChildDisconnected). Why not leaving it as kNullProcessHandle and test that
instead?

[Alexei Svitkine (slow), 2014/06/11 19:52:28]

I'm okay with that solution too. We can expand the documentation for the
|handle| field to mention what kNullProcessHandle may mean. As far as I could
tell, I think the correct description for it would be:

// The handle to the process. May have value kNullProcessHandle if no process
// exists - either because it hasn't been started yet or it's running in the
// current process.

Then, in the other files I can check for kNullProcessHandle. Do you prefer this
approach?

[piman, 2014/06/12 17:20:30]

Yes... I think the BrowserChildProcessHost's handle needs to accurately
represent the child process it owns, not the process that created it. If no
process was launched, then the handle is NULL.

 }
 
 GpuProcessHost::~GpuProcessHost() {
   DCHECK(CalledOnValidThread());
 
   SendOutstandingReplies();
 
   // Maximum number of times the gpu process is allowed to crash in a session.
   // Once this limit is reached, any request to launch the gpu process will
   // fail.
@@ skipping 708 matching lines @@
   TRACE_EVENT0("gpu", "GpuProcessHost::OnCacheShader");
   ClientIdToShaderCacheMap::iterator iter =
       client_id_to_shader_cache_.find(client_id);
   // If the cache doesn't exist then this is an off the record profile.
   if (iter == client_id_to_shader_cache_.end())
     return;
   iter->second->Cache(GetShaderPrefixKey() + ":" + key, shader);
 }
 
 }  // namespace content