Allow overriding Chromium-branded Android resources.

The chrome_java target includes several resources that are specific to a
Chromium-branded build (e.g. the Chromium icon and app name). It's now
possible to set a value for the GYP/GN variable
android_branding_res_dirs to override the directory in which these
branding resources live. This enables easy swapping of the resources
when building, e.g., a Google Chrome-branded build.

R=yfriedman@chromium.org
TBR=thestig@chromium.org
BUG=520794,474747

Review URL: https://codereview.chromium.org/1301613002 .

Cr-Commit-Position: refs/heads/master@{#343746}

chrome/android/BUILD.gn

@@ -43,10 +43,10 @@ locale_pak_resources("chrome_locale_paks") {
 
 # GYP: //chrome/chrome.gyp:chrome_java (resources part)
 android_resources("chrome_java_resources") {
-  resource_dirs = [
-    "java/res",
-    "java/res_default",
-  ]
+  if (!defined(android_branding_res_dirs)) {
+    android_branding_res_dirs = [ "//chrome/android/java/res_chromium" ]
+  }
+  resource_dirs = [ "java/res" ] + android_branding_res_dirs
   deps = [
     ":chrome_locale_paks",
     ":chrome_strings_grd",

chrome/chrome.gyp

@@ -620,19 +620,21 @@
             '../ui/android/ui_android.gyp:ui_java',
           ],
           'variables': {
+            'variables': {
+              'android_branding_res_dirs%': ['<(java_in_dir)/res_chromium'],
+            },
             'java_in_dir': '../chrome/android/java',
             'has_java_resources': 1,
             'R_package': 'org.chromium.chrome',
             'R_package_relpath': 'org/chromium/chrome',
             # Include channel-specific resources and xml string files generated
             # from generated_resources.grd
-            'res_channel_dir': '<(java_in_dir)/res_default',
             'res_extra_dirs': [
-              '<(res_channel_dir)',
+              '<@(android_branding_res_dirs)',
               '<(SHARED_INTERMEDIATE_DIR)/chrome/java/res',
             ],
             'res_extra_files': [
-              '<!@(find <(res_channel_dir) -type f)',
+              '<!@(find <(android_branding_res_dirs) -type f)',
               '<!@pymod_do_main(grit_info <@(grit_defines) --outputs "<(SHARED_INTERMEDIATE_DIR)/chrome" app/generated_resources.grd)',
             ],
           },