Change screen content test to use 3 frames only

Change to use 3 frames for screen content test from 10 frames, to
reduce test time needed.

BUG=aomedia:506

Change-Id: Ic7b44be6f3f2b65e7035bdcf24794b814b239ad1

test/cpu_speed_test.cc

@@ -94,7 +94,7 @@ void CpuSpeedTest::TestQ0() {
 }
 
 void CpuSpeedTest::TestScreencastQ0() {
-  ::libaom_test::Y4mVideoSource video("screendata.y4m", 0, 10);
+  ::libaom_test::Y4mVideoSource video("screendata.y4m", 0, 3);
   cfg_.g_timebase = video.timebase();
   cfg_.rc_2pass_vbr_minsection_pct = 5;
   cfg_.rc_2pass_vbr_maxsection_pct = 2000;
@@ -109,7 +109,7 @@ void CpuSpeedTest::TestScreencastQ0() {
 }
 
 void CpuSpeedTest::TestTuneScreen() {
-  ::libaom_test::Y4mVideoSource video("screendata.y4m", 0, 10);
+  ::libaom_test::Y4mVideoSource video("screendata.y4m", 0, 3);
   cfg_.g_timebase = video.timebase();
   cfg_.rc_2pass_vbr_minsection_pct = 5;
   cfg_.rc_2pass_vbr_minsection_pct = 2000;