Add BlimpClientContext and factory with real and dummy implementation

blimp/client/public/BUILD.gn

 # Copyright 2016 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 if (is_android) {
   import("//build/config/android/config.gni")
   import("//build/config/android/rules.gni")
 }
 
 source_set("public") {
   sources = [
+    "blimp_client_context.h",
+    "blimp_client_context_delegate.h",
     "blimp_contents.h",
     "blimp_contents_observer.h",
     "blimp_navigation_controller.h",
   ]
 
   deps = [
     "//base",
+    "//components/keyed_service/core",
     "//url",
   ]
+
+  if (is_android) {
+    sources += [ "android/blimp_jni_registrar.h" ]
+  }
 }
 
 if (is_android) {
   android_library("public_java") {
     java_files = [
+      "android/java/src/org/chromium/blimp_public/BlimpClientContext.java",
       "android/java/src/org/chromium/blimp_public/BlimpContents.java",
       "android/java/src/org/chromium/blimp_public/BlimpContentsObserver.java",
       "android/java/src/org/chromium/blimp_public/BlimpNavigationController.java",
       "android/java/src/org/chromium/blimp_public/EmptyBlimpContentsObserver.java",
     ]
   }
 }