Create PowerMonitor early so that it is usable in reduced mode

Currently the globally accessible PowerMonitor is created and owned by
BrowserMainLoop which is not created/run in reduced. In order to allow
PowerMonitor to be used in reduced mode, it is created in
ContentMainRunner and passed to BrowserMainLoop once full browser
starts.

Bug: 968247
Change-Id: If307dcbfb7f8ff0c7d34c2f4740f4a19ec77bf20
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1635861Reviewed-by: Xi Han <hanxi@chromium.org>
Reviewed-by: John Abd-El-Malek <jam@chromium.org>
Commit-Queue: Mohamed Heikal <mheikal@chromium.org>
Cr-Commit-Position: refs/heads/master@{#664566}

content/app/content_main_runner_impl.cc

@@ -32,6 +32,8 @@
 #include "base/metrics/field_trial_params.h"
 #include "base/metrics/histogram_base.h"
 #include "base/path_service.h"
+#include "base/power_monitor/power_monitor.h"
+#include "base/power_monitor/power_monitor_device_source.h"
 #include "base/process/launch.h"
 #include "base/process/memory.h"
 #include "base/process/process.h"
@@ -949,6 +951,11 @@ int ContentMainRunnerImpl::RunServiceManager(MainFunctionParams& main_params,
       }
     }
 
+    // PowerMonitor is needed in reduced mode but is eventually passed on to
+    // BrowserMainLoop.
+    power_monitor_ = std::make_unique<base::PowerMonitor>(
+        std::make_unique<base::PowerMonitorDeviceSource>());
+
     // The thread used to start the ServiceManager is handed-off to
     // BrowserMain() which may elect to promote it (e.g. to BrowserThread::IO).
     service_manager_thread_ = BrowserTaskExecutor::CreateIOThread();
@@ -970,6 +977,7 @@ int ContentMainRunnerImpl::RunServiceManager(MainFunctionParams& main_params,
   startup_data_ = std::make_unique<StartupDataImpl>();
   startup_data_->thread = std::move(service_manager_thread_);
   startup_data_->service_manager_context = service_manager_context_.get();
+  startup_data_->power_monitor = std::move(power_monitor_);
   main_params.startup_data = startup_data_.get();
   return RunBrowserProcessMain(main_params, delegate_);
 }

content/app/content_main_runner_impl.h

@@ -10,6 +10,7 @@
 #include "base/callback_forward.h"
 #include "base/memory/scoped_refptr.h"
 #include "base/metrics/field_trial.h"
+#include "base/power_monitor/power_monitor.h"
 #include "build/build_config.h"
 #include "content/browser/service_manager/service_manager_context.h"
 #include "content/browser/startup_data_impl.h"
@@ -57,6 +58,7 @@ class ContentMainRunnerImpl : public ContentMainRunner {
   std::unique_ptr<base::FieldTrialList> field_trial_list_;
   std::unique_ptr<BrowserProcessSubThread> service_manager_thread_;
   std::unique_ptr<ServiceManagerContext> service_manager_context_;
+  std::unique_ptr<base::PowerMonitor> power_monitor_;
 #endif  // !defined(CHROME_MULTIPLE_DLL_CHILD)
 
   // True if the runner has been initialized.

content/browser/browser_main_loop.cc

@@ -566,6 +566,7 @@ void BrowserMainLoop::Init() {
     // resets it).
     io_thread_ = std::move(startup_data->thread);
     service_manager_context_ = startup_data->service_manager_context;
+    power_monitor_ = std::move(startup_data->power_monitor);
   }
 
   parts_.reset(
@@ -691,10 +692,10 @@ void BrowserMainLoop::PostMainMessageLoopStart() {
   }
   {
     TRACE_EVENT0("startup", "BrowserMainLoop::Subsystem:PowerMonitor");
-    std::unique_ptr<base::PowerMonitorSource> power_monitor_source(
-        new base::PowerMonitorDeviceSource());
-    power_monitor_.reset(
-        new base::PowerMonitor(std::move(power_monitor_source)));
+    if (!power_monitor_) {
+      power_monitor_ = std::make_unique<base::PowerMonitor>(
+          std::make_unique<base::PowerMonitorDeviceSource>());
+    }
   }
   {
     TRACE_EVENT0("startup", "BrowserMainLoop::Subsystem:HighResTimerManager");

content/browser/startup_data_impl.h

@@ -7,6 +7,7 @@
 
 #include <memory>
 
+#include "base/power_monitor/power_monitor.h"
 #include "content/browser/browser_process_sub_thread.h"
 #include "content/common/content_export.h"
 #include "content/public/browser/startup_data.h"
@@ -22,6 +23,7 @@ struct CONTENT_EXPORT StartupDataImpl : public StartupData {
 
   std::unique_ptr<BrowserProcessSubThread> thread;
   ServiceManagerContext* service_manager_context;
+  std::unique_ptr<base::PowerMonitor> power_monitor;
 };
 
 }  // namespace content