Add missing .h files to .gn files that have a .cc file next to it in the gn file already.

third_party/WebKit/Source/core/inspector/BUILD.gn

 # Copyright 2014 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/bindings/bindings.gni")
 import("//third_party/WebKit/Source/core/core.gni")
 import("//third_party/inspector_protocol/inspector_protocol.gni")
 import("//v8/gni/v8.gni")
 
 _inspector_protocol_dir = "//third_party/inspector_protocol"
@@ skipping 16 matching lines @@
     "InspectedFrames.cpp",
     "InspectedFrames.h",
     "InspectorAnimationAgent.cpp",
     "InspectorAnimationAgent.h",
     "InspectorApplicationCacheAgent.cpp",
     "InspectorApplicationCacheAgent.h",
     "InspectorBaseAgent.h",
     "InspectorCSSAgent.cpp",
     "InspectorCSSAgent.h",
     "InspectorDOMAgent.cpp",
+    "InspectorDOMAgent.h",
     "InspectorDOMDebuggerAgent.cpp",
     "InspectorDOMDebuggerAgent.h",
     "InspectorHighlight.cpp",
     "InspectorHighlight.h",
     "InspectorHistory.cpp",
     "InspectorHistory.h",
     "InspectorInputAgent.cpp",
     "InspectorInputAgent.h",
     "InspectorInstrumentation.cpp",
     "InspectorInstrumentation.h",
@@ skipping 210 matching lines @@
   outputs = [
     output_file,
   ]
 
   args = [
     rebase_path("browser_protocol.json", root_build_dir),
     rebase_path(v8_inspector_js_protocol, root_build_dir),
     rebase_path(output_file, root_build_dir),
   ]
 }