[DevTools] [PowerProfiler] Fix for browser crash with active timeline recording for capturing power.

content/browser/power_profiler/power_profiler_service.cc

 // Copyright 2014 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/power_profiler/power_profiler_service.h"
 
 #include "base/bind.h"
 #include "base/message_loop/message_loop.h"
 #include "base/threading/sequenced_worker_pool.h"
 #include "content/public/browser/browser_thread.h"
@@ skipping 42 matching lines @@
 void PowerProfilerService::AddObserver(PowerProfilerObserver* observer) {
   if (status_ == UNINITIALIZED)
     return;
 
   observers_.AddObserver(observer);
   if (status_ != PROFILING)
     Start();
 }
 
 void PowerProfilerService::RemoveObserver(PowerProfilerObserver* observer) {
+  if (!observers_.might_have_observers())

[jam, 2014/06/19 16:42:34]

why is this needed?

[vivekg, 2014/06/19 17:46:02]

This was added after the discussion as per the
https://codereview.chromium.org/332623003/#msg24

[jam, 2014/06/20 05:59:46]

I don't follow that conversation, can you explained in a self-contained comment?

I'm looking at ObserverList::RemoveObserver code in
https://code.google.com/p/chromium/codesearch#chromium/src/base/observer_list...
and it doesn't assert that the given pointer is in the list.

+    return;
+
   observers_.RemoveObserver(observer);
 
   if (!observers_.might_have_observers())
     Stop();
 }
 
 void PowerProfilerService::Start() {
   DCHECK(status_ == INITIALIZED);
   status_ = PROFILING;
 
@@ skipping 27 matching lines @@
 
   // Get data and notify.
   PowerEventVector events = data_provider_->GetData();
   if (events.size() != 0) {
     BrowserThread::PostTask(BrowserThread::UI, FROM_HERE, base::Bind(
         &PowerProfilerService::Notify, base::Unretained(this), events));
   }
 }
 
 }  // namespace content