Move fake-handle frame creation into test target.

Renames CreateFakeNativeHandleFrame to FakeNativeHandle::CreateFrame and
moves into test.gyp target 'fake_video_frames' which contains previous
frame_generator target.

Removes unused warnings from includers of
webrtc/test/fake_texture_frame.h which did not use the function above.

BUG=webrtc:5398
R=kjellander@webrtc.org
TBR=stefan@webrtc.org

Review URL: https://codereview.webrtc.org/1554223002 .

Cr-Commit-Position: refs/heads/master@{#11149}
diff --git a/webrtc/modules/modules.gyp b/webrtc/modules/modules.gyp
index d1fcebb..e3698e2 100644
--- a/webrtc/modules/modules.gyp
+++ b/webrtc/modules/modules.gyp
@@ -148,7 +148,7 @@
                 '<(webrtc_root)/modules/video_coding/codecs/vp8/vp8.gyp:webrtc_vp8',
                 '<(webrtc_root)/modules/video_coding/codecs/vp9/vp9.gyp:webrtc_vp9',
                 '<(webrtc_root)/system_wrappers/system_wrappers.gyp:system_wrappers',
-                '<(webrtc_root)/test/test.gyp:frame_generator',
+                '<(webrtc_root)/test/test.gyp:fake_video_frames',
                 '<(webrtc_root)/test/test.gyp:rtp_test_utils',
                 '<(webrtc_root)/test/test.gyp:test_support_main',
                 '<(webrtc_root)/test/webrtc_test_common.gyp:webrtc_test_common',