Files app: Enable gzip compression for resources

Enable gzip compression for resources on the following apps: Files,
Gallery, Video and Audio Player. For reducing the disk usage on the
ChromeOS root partition.

Change ExecuteCodeFunction::LoadFile() to use
ResourceBundle::LoadDataResourceString() to load resources that may be
compressed or not.

Test: ui_base_unittests --gtest_filter='ResourceBundleImageTest.*'
Bug: 715912, 1003433
Change-Id: I307d16e075c157784a3daad9f2a4c7faf4736cc2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1873827
Auto-Submit: Luciano Pacheco <lucmult@chromium.org>
Reviewed-by: Ben Wells <benwells@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Reviewed-by: Demetrios Papadopoulos <dpapad@chromium.org>
Commit-Queue: Luciano Pacheco <lucmult@chromium.org>
Cr-Commit-Position: refs/heads/master@{#712451}

extensions/browser/api/execute_code_function.cc

@@ -239,11 +239,9 @@ bool ExecuteCodeFunction::LoadFile(const std::string& file,
       component_extension_resource_manager->IsComponentExtensionResource(
           resource_.extension_root(), resource_.relative_path(),
           &resource_id)) {
-    DCHECK(!ui::ResourceBundle::GetSharedInstance().IsGzipped(resource_id));
-    base::StringPiece resource =
-        ui::ResourceBundle::GetSharedInstance().GetRawDataResource(resource_id);
-    std::unique_ptr<std::string> data(
-        new std::string(resource.data(), resource.size()));
+    auto data = std::make_unique<std::string>(
+        ui::ResourceBundle::GetSharedInstance().LoadDataResourceString(
+            resource_id));
 
     base::PostTaskAndReplyWithResult(
         FROM_HERE,

ui/base/resource/resource_bundle.cc

@@ -157,6 +157,7 @@ void DecompressIfNeeded(base::StringPiece data, std::string* output) {
     bool success = BrotliDecompress(data, output);
     DCHECK(success);
   } else {
+    // Assume the raw data is not compressed.
     data.CopyToString(output);
   }
 }

ui/base/resource/resource_bundle_unittest.cc

@@ -513,6 +513,9 @@ TEST_F(ResourceBundleImageTest, LoadDataResourceString) {
 
   // Resource ID 8 is Gzip compressed, expect it to be uncompressed.
   EXPECT_EQ("this is id 8", resource_bundle->LoadDataResourceString(8));
+
+  // Resource ID 4 is plain text (not compressed), expect to return as-is.
+  EXPECT_EQ("this is id 4", resource_bundle->LoadDataResourceString(4));
 }
 
 TEST_F(ResourceBundleImageTest, GetRawDataResource) {