Use bilinear scaling for tab capture on Mac

Macbook pros using Intel graphic chips are using the synchronous
readback path. This path is using point sampling and shows
noticiable scaling artifacts.

Changing this to bilinear to match asynchronous	case.

BUG=168917


Review URL: https://chromiumcodereview.appspot.com/11826036

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@176001 0039d316-1c4b-4281-b951-d872f2087c98

content/browser/renderer_host/compositing_iosurface_mac.mm

@@ -668,6 +668,8 @@ bool CompositingIOSurfaceMac::SynchronousCopyTo(
   glUniform1i(blit_rgb_sampler_location_, texture_unit);
   glActiveTexture(GL_TEXTURE0 + texture_unit);
   glBindTexture(GL_TEXTURE_RECTANGLE_ARB, texture_);
+  glTexParameterf(GL_TEXTURE_RECTANGLE_ARB, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
+  glTexParameterf(GL_TEXTURE_RECTANGLE_ARB, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
 
   SurfaceQuad quad;
   quad.set_rect(0.0f, 0.0f, dst_pixel_size.width(), dst_pixel_size.height());