[iOS] Load chrome_300_percent.pak file on @3x devices.

This CL adds support for loading assets from the chrome_300_percent.pak
file on devices that support @3x scale.

BUG=423762

Review URL: https://codereview.chromium.org/646773004

Cr-Commit-Position: refs/heads/master@{#301142}

ui/base/resource/resource_bundle.cc

@@ -469,6 +469,7 @@ base::StringPiece ResourceBundle::GetRawDataResourceForScale(
   for (size_t i = 0; i < data_packs_.size(); i++) {
     if ((data_packs_[i]->GetScaleFactor() == ui::SCALE_FACTOR_100P ||
          data_packs_[i]->GetScaleFactor() == ui::SCALE_FACTOR_200P ||
+         data_packs_[i]->GetScaleFactor() == ui::SCALE_FACTOR_300P ||
          data_packs_[i]->GetScaleFactor() == ui::SCALE_FACTOR_NONE) &&
         data_packs_[i]->GetStringPiece(static_cast<uint16>(resource_id),
                                        &data))

ui/base/resource/resource_bundle_ios.mm

@@ -54,11 +54,9 @@ void ResourceBundle::LoadCommonResources() {
                         SCALE_FACTOR_200P);
   }
 
-  // TODO(rohitrao): Add a chrome_300_percent file and load it here.  For now,
-  // we are simply falling back to the 200P resources. http://crbug.com/413300.
   if (IsScaleFactorSupported(SCALE_FACTOR_300P)) {
-    AddDataPackFromPath(GetResourcesPakFilePath(@"chrome_200_percent", nil),
-                        SCALE_FACTOR_200P);
+    AddDataPackFromPath(GetResourcesPakFilePath(@"chrome_300_percent", nil),
+                        SCALE_FACTOR_300P);
   }
 }