Minimize PowerSaveBlocker usage during uploading data.

content/browser/loader/power_save_block_resource_throttle.cc

 // Copyright (c) 2013 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/loader/power_save_block_resource_throttle.h"
 
+#include "base/bind.h"
+#include "base/memory/weak_ptr.h"
+#include "base/message_loop.h"
 #include "content/public/browser/power_save_blocker.h"
 
 namespace content {
 
-PowerSaveBlockResourceThrottle::PowerSaveBlockResourceThrottle(
-    const std::string& reason) {
-  power_save_blocker_ = PowerSaveBlocker::Create(
-      PowerSaveBlocker::kPowerSaveBlockPreventAppSuspension, reason);
+namespace {
+
+const int kPowerSaveBlockDelaySeconds = 30;
+
+}  // namespace
+
+class PowerSaveBlockResourceThrottle::PowerSaveBlockerOwner {

[darin (slow to review), 2013/02/12 19:20:05]

I don't understand why you bothered to create this nested class.  You can just
fold this functionality into the PowerSaveBlockResourceThrottle class.

[hashimoto, 2013/02/13 08:02:35]

I was trying to introduce more complicated mechanism like polling
URLRequest::GetUploadProgress(), and thought having a nested class was a good
way to handle canceling. (i.e. just calling scoped_ptr<>::reset is enough to
cancel all in-fly operations)

Abandoned this nested class since what the current patch does is simply delaying
power save block.

+ public:
+  PowerSaveBlockerOwner()
+      : weak_ptr_factory_(ALLOW_THIS_IN_INITIALIZER_LIST(this)) {
+    // Delay PowerSaveBlocker activation to dismiss small requests.
+    MessageLoop::current()->PostDelayedTask(
+        FROM_HERE,
+        base::Bind(&PowerSaveBlockerOwner::ActivatePowerSaveBlocker,
+                   weak_ptr_factory_.GetWeakPtr()),
+        base::TimeDelta::FromSeconds(kPowerSaveBlockDelaySeconds));
+  }
+
+  ~PowerSaveBlockerOwner() {}
+
+  void ActivatePowerSaveBlocker() {
+    power_save_blocker_ = PowerSaveBlocker::Create(
+        PowerSaveBlocker::kPowerSaveBlockPreventAppSuspension,
+        "Uploading data.");
+  }
+
+ private:
+  scoped_ptr<PowerSaveBlocker> power_save_blocker_;
+  base::WeakPtrFactory<PowerSaveBlockerOwner> weak_ptr_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(PowerSaveBlockerOwner);
+};
+
+PowerSaveBlockResourceThrottle::PowerSaveBlockResourceThrottle() {
 }
 
 PowerSaveBlockResourceThrottle::~PowerSaveBlockResourceThrottle() {
 }
 
+void PowerSaveBlockResourceThrottle::WillStartRequest(bool* defer) {
+  power_save_blocker_owner_.reset(new PowerSaveBlockerOwner());
+}
+
 void PowerSaveBlockResourceThrottle::WillProcessResponse(bool* defer) {
   // Stop blocking power save after request finishes.
-  power_save_blocker_.reset();
+  power_save_blocker_owner_.reset();
 }
 
 }  // namespace content