Introduce WebRemoteFrameBase to break dependencies on WebRemoteFrameImpl.

third_party/WebKit/Source/core/frame/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.
 
 import("//third_party/WebKit/Source/core/core.gni")
 
 blink_core_sources("frame") {
   sources = [
     "BarProp.cpp",
     "BarProp.h",
@@ skipping 101 matching lines @@
     "SuspendableScriptExecutor.cpp",
     "SuspendableScriptExecutor.h",
     "SuspendableTimer.cpp",
     "SuspendableTimer.h",
     "UseCounter.cpp",
     "UseCounter.h",
     "VisualViewport.cpp",
     "VisualViewport.h",
     "WebLocalFrameBase.cpp",
     "WebLocalFrameBase.h",
+    "WebRemoteFrameBase.cpp",
+    "WebRemoteFrameBase.h",
     "csp/CSPDirective.h",
     "csp/CSPDirectiveList.cpp",
     "csp/CSPDirectiveList.h",
     "csp/CSPSource.cpp",
     "csp/CSPSource.h",
     "csp/ContentSecurityPolicy.cpp",
     "csp/ContentSecurityPolicy.h",
     "csp/MediaListDirective.cpp",
     "csp/MediaListDirective.h",
     "csp/SourceListDirective.cpp",
     "csp/SourceListDirective.h",
   ]
 
   configs += [
     # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
     "//build/config/compiler:no_size_t_to_int_warning",
   ]
 }