Implement --ozone-platform flag to select OzonePlatform implementation at runtime

ui/base/ozone/ozone.gyp

Index: ui/base/ozone/ozone.gyp
diff --git a/ui/base/ozone/ozone.gyp b/ui/base/ozone/ozone.gyp
index 19c466bb0b12b5bfaad2769dc9847fe5480151fb..008e4eb90d0a3a161ccd23829dffeb73f9059f2c 100644
--- a/ui/base/ozone/ozone.gyp
+++ b/ui/base/ozone/ozone.gyp
@@ -21,7 +21,11 @@
       'defines': [
         'OZONE_IMPLEMENTATION',
       ],
+      'variables': {
+        'platform_list_file': '<(SHARED_INTERMEDIATE_DIR)/ui/base/ozone/ozone_platform_list.cc',
+      },
       'sources': [
+        '<(platform_list_file)',
         'ozone_platform.cc',
         'ozone_platform.h',
         'ozone_switches.cc',
@@ -32,13 +36,46 @@
         'platform/test/ozone_platform_test.h',
         '<@(external_ozone_platform_files)',
       ],
+      'actions': [
+        {
+          'action_name': 'generate_ozone_platform_list',
+          'variables': {
+            'generator_path': 'generate_ozone_platform_list.py',
+          },
+          'inputs': [
+            '<(generator_path)',
+          ],
+          'outputs': [
+            '<(platform_list_file)',
+          ],
+          'action': [
+            'python',
+            '<(generator_path)',
+            '--output_file=<(platform_list_file)',
+            '--default=<(ozone_platform)',
+            '<@(ozone_platforms)',
+          ],
+        },
+      ],
       'conditions': [
-        ['ozone_platform != "dri"', {
+        ['<(ozone_platform_dri)==1', {
+          'variables': {
+            'ozone_platforms': [
+              'dri'
+            ]
+          }
+        }, {  # ozone_platform_dri==0

[kalyank, 2013/10/25 21:09:30]

If ozone is enabled, we always enable ozone_platform_dri and test in
common.gypi. Do we still need ozone_platform_dri = 0 case ?. I mean is it even
possible to have them disabled when support for ozone is enabled.

[spang, 2013/10/25 21:14:14]

Yes, because everything from common.gypi is a default value that can be
overridden:

GYP_DEFINES="ozone_platform_dri=0" gclient runhooks

would remove DRI support from the build.

           'sources/': [
             ['exclude', '^platform/dri/'],
           ]
         }],
-        ['ozone_platform != "test"', {
+        ['<(ozone_platform_test)==1', {
+          'variables': {
+            'ozone_platforms': [
+              'test'
+            ],
+          }
+        }, {  # ozone_platform_test==0
           'sources/': [
             ['exclude', '^platform/test/'],
           ]