Fix BuildConfig generation for internal builds

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=140210128

demo/build.gradle

@@ -37,23 +37,17 @@ android {
         abortOnError false
     }
 
-    flavorDimensions "extensions"
-
     productFlavors {
-        noExtns {
-            dimension "extensions"
-        }
-        extns {
-            dimension "extensions"
-        }
+        noExtensions
+        withExtensions
     }
 
 }
 
 dependencies {
     compile project(':library')
-    extnsCompile project(path: ':extension-ffmpeg')
-    extnsCompile project(path: ':extension-flac')
-    extnsCompile project(path: ':extension-opus')
-    extnsCompile project(path: ':extension-vp9')
+    withExtensionsCompile project(path: ':extension-ffmpeg')
+    withExtensionsCompile project(path: ':extension-flac')
+    withExtensionsCompile project(path: ':extension-opus')
+    withExtensionsCompile project(path: ':extension-vp9')
 }

demo/src/main/java/com/google/android/exoplayer2/demo/DemoApplication.java

@@ -46,9 +46,7 @@ public class DemoApplication extends Application {
   }
 
   public boolean useExtensionRenderers() {
-    // We should return BuildConfig.FLAVOR_extensions.equals("extns") here, but this is currently
-    // incompatible with a Google internal build system.
-    return true;
+    return BuildConfig.FLAVOR.equals("withExtensions");
   }
 
 }