Use no-op statistics collecting object for WebView.

WebView does not gather data_reduction_proxy related
statistics at the moment. WebView's statistics object writes
the data to pref service which does not upload the data to
anywhere.

BUG=b/17998706

Review URL: https://codereview.chromium.org/651443005

Cr-Commit-Position: refs/heads/master@{#300613}

android_webview/browser/aw_browser_context.cc

@@ -20,6 +20,7 @@
 #include "components/data_reduction_proxy/core/browser/data_reduction_proxy_params.h"
 #include "components/data_reduction_proxy/core/browser/data_reduction_proxy_prefs.h"
 #include "components/data_reduction_proxy/core/browser/data_reduction_proxy_settings.h"
+#include "components/data_reduction_proxy/core/browser/data_reduction_proxy_statistics_prefs.h"
 #include "components/user_prefs/user_prefs.h"
 #include "components/visitedlink/browser/visitedlink_master.h"
 #include "content/public/browser/browser_thread.h"
@@ -94,6 +95,10 @@ void AwBrowserContext::SetDataReductionProxyEnabled(bool enabled) {
       context->GetDataReductionProxySettings();
   if (proxy_settings == NULL)
     return;
+
+  context->CreateDataReductionProxyStatisticsIfNecessary();
+  proxy_settings->SetDataReductionProxyStatisticsPrefs(
+      context->data_reduction_proxy_statistics_.get());
   proxy_settings->SetDataReductionProxyEnabled(data_reduction_proxy_enabled_);
 }
 
@@ -293,4 +298,19 @@ void AwBrowserContext::RebuildTable(
   enumerator->OnComplete(true);
 }
 
+void AwBrowserContext::CreateDataReductionProxyStatisticsIfNecessary() {
+  DCHECK(user_pref_service_.get());
+
+  if (!data_reduction_proxy_statistics_.get()) {
+    // We don't care about commit_delay for now. It is just a dummy value.
+    base::TimeDelta commit_delay = base::TimeDelta::FromMinutes(60);
+    data_reduction_proxy_statistics_ =
+        scoped_ptr<data_reduction_proxy::DataReductionProxyStatisticsPrefs>(
+            new data_reduction_proxy::DataReductionProxyStatisticsPrefs(
+                user_pref_service_.get(),
+                base::MessageLoopProxy::current(),
+                commit_delay));
+  }
+}
+
 }  // namespace android_webview

android_webview/browser/aw_browser_context.h

@@ -30,6 +30,7 @@ class WebContents;
 namespace data_reduction_proxy {
 class DataReductionProxyConfigurator;
 class DataReductionProxySettings;
+class DataReductionProxyStatisticsPrefs;
 }
 
 namespace net {
@@ -116,6 +117,7 @@ class AwBrowserContext : public content::BrowserContext,
       const scoped_refptr<URLEnumerator>& enumerator) override;
 
  private:
+  void CreateDataReductionProxyStatisticsIfNecessary();
   static bool data_reduction_proxy_enabled_;
 
   // The file path where data for this context is persisted.
@@ -136,6 +138,8 @@ class AwBrowserContext : public content::BrowserContext,
 
   scoped_ptr<data_reduction_proxy::DataReductionProxyConfigurator>
       data_reduction_proxy_configurator_;
+  scoped_ptr<data_reduction_proxy::DataReductionProxyStatisticsPrefs>
+      data_reduction_proxy_statistics_;
   scoped_ptr<data_reduction_proxy::DataReductionProxySettings>
       data_reduction_proxy_settings_;