MojoWebUIBrowserTest: Allow compressing of test resources.

Previously the code assumed, via the usage of
l10n_util::GetStringUTF16, that the underlying resources at
chrome/test/data/webui_test_resources.grd are not compressed.

Moreover, using l10n_util::GetStringUTF16() is not designed for fetching
a file's content and was somewhat misused here.

This is one of many CLs, in preparation of compressing all HTML, JS,
CSS, SVG files by default (meaning without requiring compress="gzip"
to be specified).

Bug: 1068407
Change-Id: I77fe0f9966f6e277288838c42260433c34bd403c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2146090
Auto-Submit: dpapad <dpapad@chromium.org>
Commit-Queue: Ken Rockot <rockot@google.com>
Reviewed-by: Ken Rockot <rockot@google.com>
Cr-Commit-Position: refs/heads/master@{#758538}

chrome/test/base/mojo_web_ui_browser_test.cc

@@ -23,7 +23,6 @@
 #include "mojo/public/cpp/bindings/pending_receiver.h"
 #include "mojo/public/cpp/bindings/receiver.h"
 #include "services/service_manager/public/cpp/binder_map.h"
-#include "ui/base/l10n/l10n_util.h"
 #include "ui/base/resource/resource_bundle.h"
 
 namespace {
@@ -129,12 +128,16 @@ void MojoWebUIBrowserTest::BrowsePreload(const GURL& browse_to) {
   content::WebContents* web_contents =
       browser()->tab_strip_model()->GetActiveWebContents();
   if (use_mojo_lite_bindings_) {
+    std::string test_mojo_lite_js =
+        ui::ResourceBundle::GetSharedInstance().LoadDataResourceString(
+            IDR_WEB_UI_TEST_MOJO_LITE_JS);
     web_contents->GetMainFrame()->ExecuteJavaScriptForTests(
-        l10n_util::GetStringUTF16(IDR_WEB_UI_TEST_MOJO_LITE_JS),
-        base::NullCallback());
+        base::UTF8ToUTF16(test_mojo_lite_js), base::NullCallback());
   } else {
+    std::string test_mojo_js =
+        ui::ResourceBundle::GetSharedInstance().LoadDataResourceString(
+            IDR_WEB_UI_TEST_MOJO_JS);
     web_contents->GetMainFrame()->ExecuteJavaScriptForTests(
-        l10n_util::GetStringUTF16(IDR_WEB_UI_TEST_MOJO_JS),
-        base::NullCallback());
+        base::UTF8ToUTF16(test_mojo_js), base::NullCallback());
   }
 }