Add a new target for GmsCore integration.

Add a new target for GmsCore integration to let WebView code depend on
GmsCore without depending on //android_webview/android_webview_java.
Note that we don't remove PlatformServiceBridge from the
android_webview_java target yet as that would break downstream.

BUG=657314

Review-Url: https://codereview.chromium.org/2566903003
Cr-Commit-Position: refs/heads/master@{#437878}

android_webview/BUILD.gn

@@ -597,6 +597,9 @@ android_library("android_webview_java") {
     "java/src/org/chromium/android_webview/JsResultReceiver.java",
     "java/src/org/chromium/android_webview/NullAwViewMethods.java",
     "java/src/org/chromium/android_webview/OverScrollGlow.java",
+
+    # TODO(gsennton): remove PlatformServiceBridge after downstream has been updated to depend on
+    # android_webview_platform_services_java
     "java/src/org/chromium/android_webview/PlatformServiceBridge.java",
     "java/src/org/chromium/android_webview/PopupTouchHandleDrawable.java",
     "java/src/org/chromium/android_webview/ResourcesContextWrapperFactory.java",
@@ -681,6 +684,17 @@ java_strings_grd("strings_grd") {
   ]
 }
 
+# Separate target to allow for a dependency on GmsCore without pulling in all of
+# android_webview_java.
+android_library("android_webview_platform_services_java") {
+  java_files =
+      [ "java/src/org/chromium/android_webview/PlatformServiceBridge.java" ]
+
+  deps = [
+    "//base:base_java",
+  ]
+}
+
 if (!use_webview_internal_framework) {
   system_webview_apk_tmpl("system_webview_apk") {
     android_manifest = system_webview_android_manifest