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/page/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("page") {
   sources = [
     "AutoscrollController.cpp",
     "AutoscrollController.h",
     "ChromeClient.cpp",
     "ChromeClient.h",
     "ContextMenuController.cpp",
+    "ContextMenuController.h",
     "ContextMenuProvider.h",
     "CreateWindow.cpp",
     "CreateWindow.h",
     "CustomContextMenuProvider.cpp",
     "CustomContextMenuProvider.h",
     "DragController.cpp",
+    "DragController.h",
     "DragData.cpp",
     "EventWithHitTestResults.h",
     "FocusChangedObserver.cpp",
     "FocusChangedObserver.h",
     "FocusController.cpp",
+    "FocusController.h",
     "FrameTree.cpp",
+    "FrameTree.h",
     "Page.cpp",
     "Page.h",
     "PageAnimator.cpp",
     "PageAnimator.h",
     "PagePopupClient.cpp",
     "PagePopupClient.h",
     "PagePopupController.cpp",
     "PagePopupController.h",
     "PagePopupSupplement.cpp",
     "PagePopupSupplement.h",
     "PageVisibilityNotifier.cpp",
     "PageVisibilityNotifier.h",
     "PageVisibilityObserver.h",
     "PageVisibilityState.cpp",
     "PointerLockController.cpp",
     "PointerLockController.h",
     "PopupOpeningObserver.h",
     "PrintContext.cpp",
+    "PrintContext.h",
     "ScopedPageSuspender.cpp",
     "ScopedPageSuspender.h",
     "SpatialNavigation.cpp",
+    "SpatialNavigation.h",
     "TouchAdjustment.cpp",
     "TouchAdjustment.h",
     "TouchDisambiguation.cpp",
     "TouchDisambiguation.h",
     "WindowFeatures.cpp",
     "scrolling/OverscrollController.cpp",
     "scrolling/OverscrollController.h",
     "scrolling/RootScrollerController.cpp",
     "scrolling/RootScrollerController.h",
     "scrolling/RootScrollerUtil.cpp",
@@ skipping 14 matching lines @@
     "scrolling/TopDocumentRootScrollerController.h",
     "scrolling/ViewportScrollCallback.cpp",
     "scrolling/ViewportScrollCallback.h",
   ]
 
   configs += [
     # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
     "//build/config/compiler:no_size_t_to_int_warning",
   ]
 }