Introduce ChromeVR to Chrome on Android (behind a build flag)

chrome/android/BUILD.gn

Index: chrome/android/BUILD.gn
diff --git a/chrome/android/BUILD.gn b/chrome/android/BUILD.gn
index e88bf3492d82c3e9f8a0afa28a1b562bf4a61359..3cdc0e18be94aa6f6c80c217779183ae147e57b2 100644
--- a/chrome/android/BUILD.gn
+++ b/chrome/android/BUILD.gn
@@ -248,6 +248,16 @@ android_library("chrome_java") {
       "//components/web_contents_delegate_android:web_contents_delegate_android_java",
     ]
   }
+
+  # VrActivity currently depends on ChromeTabbedActivity which is part of
+  # android_java_ui.
+  if (enable_vr_shell && android_java_ui) {
+    java_files += chrome_vr_java_sources
+    deps += [
+      "//third_party/gvr-android-sdk:gvr_base_java",
+      "//third_party/gvr-android-sdk:gvr_common_java",
+    ]
+  }
 }
 
 # GYP: //chrome/chrome_browser.gypi:activity_type_ids_java