gpu testing: Handle non-integral device pixel ratio.

Device pixel ratio is used to scale test rect and sampling locations.
It can be non-integral on some devices. For example it is 1.325 on
Nexus 7. The scaled quantities - dimensions of screenshot and sampled
pixel locations - need to be converted to integers before they can
be used.

BUG=368495

Review URL: https://codereview.chromium.org/303113004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@273951 0039d316-1c4b-4281-b951-d872f2087c98

content/test/gpu/gpu_tests/cloud_storage_test_base.py

@@ -24,8 +24,8 @@ error_image_cloud_storage_bucket = 'chromium-browser-gpu-tests'
 def _CompareScreenshotSamples(screenshot, expectations, device_pixel_ratio):
   for expectation in expectations:
     location = expectation["location"]
-    x = location[0] * device_pixel_ratio
-    y = location[1] * device_pixel_ratio
+    x = int(location[0] * device_pixel_ratio)
+    y = int(location[1] * device_pixel_ratio)
 
     if x < 0 or y < 0 or x > screenshot.width or y > screenshot.height:
       raise page_test.Failure(

content/test/gpu/gpu_tests/gpu_rasterization.py

@@ -49,7 +49,7 @@ class _GpuRasterizationValidator(cloud_storage_test_base.ValidatorBase):
 
     device_pixel_ratio = tab.EvaluateJavaScript('window.devicePixelRatio')
     if hasattr(page, 'test_rect'):
-      test_rect = [x * device_pixel_ratio for x in page.test_rect]
+      test_rect = [int(x * device_pixel_ratio) for x in page.test_rect]
       screenshot = screenshot.Crop(
           test_rect[0], test_rect[1],
           test_rect[2], test_rect[3])