Speculative workaround for VS 2015 code-gen bug

chrome/browser/power/process_power_collector.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 "chrome/browser/power/process_power_collector.h"
 
 #include <utility>
 
 #include "base/memory/ptr_util.h"
 #include "base/process/process_handle.h"
@@ skipping 76 matching lines @@
 }
 
 void ProcessPowerCollector::StartTimer() {
   DCHECK(!timer_.IsRunning());
   timer_.Start(FROM_HERE,
                base::TimeDelta::FromSeconds(kSecondsPerSample),
                this,
                &ProcessPowerCollector::HandleUpdateTimeout);
 }
 
+// Work around VS 2015 code-gen bug, seen in Update 2 and Update 3.
+// crbug.com/640588
+#if defined(COMPILER_MSVC)
+#pragma optimize("", off)
+#endif
 double ProcessPowerCollector::UpdatePowerConsumption() {
   double total_cpu_percent = SynchronizeProcesses();
 
   // Invalidate the process for the next cycle.
   for (auto& metrics : metrics_map_)
     metrics.second->set_seen_this_cycle(false);
 
   RecordCpuUsageByOrigin(total_cpu_percent);
   return total_cpu_percent;
 }
 
 void ProcessPowerCollector::HandleUpdateTimeout() {
   UpdatePowerConsumption();
 }
+#if defined(COMPILER_MSVC)
+#pragma optimize("", on)
+#endif
 
 double ProcessPowerCollector::SynchronizeProcesses() {
   // Update all tabs.
   for (TabContentsIterator it; !it.done(); it.Next()) {
     content::RenderProcessHost* render_process = it->GetRenderProcessHost();
     // Skip incognito web contents.
     if (render_process->GetBrowserContext()->IsOffTheRecord())
       continue;
     UpdateProcessInMap(render_process, it->GetLastCommittedURL().GetOrigin());
   }
@@ skipping 70 matching lines @@
 #endif
         origin, Profile::FromBrowserContext(rph->GetBrowserContext()));
   }
 
   PerProcessData* process_data = metrics_map_[handle].get();
   process_data->set_last_cpu_percent(std::max(0.0,
       cpu_usage_callback_.is_null() ? process_data->metrics()->GetCPUUsage()
                                     : cpu_usage_callback_.Run(handle)));
   process_data->set_seen_this_cycle(true);
 }