Update gypi in extensions after move and removal of headers.

Fixes warnings in the gyp msvs-ninja generator.

Followup to
https://codereview.chromium.org/892923002 (guest_view_messages.h)
https://codereview.chromium.org/913393003 (extension_view.js)
https://codereview.chromium.org/820513002 (surface_worker.js,
    and surface_view.js)
https://codereview.chromium.org/654043002 (web_view.js,
    web_view_events.js and web_view_experimental.js)

R=fsamuel@chromium.org,kalman@chromium.org,apacible@chromium.org,rockot@chromium.org
BUG=459058,444869,459680,434226

Review URL: https://codereview.chromium.org/952513002

Cr-Commit-Position: refs/heads/master@{#317767}

extensions/extensions.gypi

@@ -94,7 +94,7 @@
       'common/file_util.h',
       'common/guest_view/guest_view_constants.cc',
       'common/guest_view/guest_view_constants.h',
-      'common/guest_view_messages.h',
+      'common/guest_view/guest_view_messages.h',
       'common/host_id.cc',
       'common/host_id.h',
       'common/image_util.cc',
@@ -907,11 +907,11 @@
       'renderer/resources/uncaught_exception_handler.js',
       'renderer/resources/unload_event.js',
       'renderer/resources/utils.js',
-      'renderer/resources/extensions/extension_view.js',
-      'renderer/resources/extensions/surface_worker.js',
-      'renderer/resources/extensions/web_view.js',
-      'renderer/resources/extensions/web_view_events.js',
-      'renderer/resources/extensions/web_view_experimental.js',
+      'renderer/resources/guest_view/extension_view.js',
+      'renderer/resources/guest_view/surface_view.js',
+      'renderer/resources/guest_view/web_view.js',
+      'renderer/resources/guest_view/web_view_events.js',
+      'renderer/resources/guest_view/web_view_experimental.js',
       'renderer/resources/web_request_custom_bindings.js',
       'renderer/resources/web_request_internal_custom_bindings.js',
       'renderer/runtime_custom_bindings.cc',