Fix fuzzy color check in ClearTest.

This test was failing on some systems because of overly stringent
color expectations.

BUG=angle:809

Change-Id: I817de315ff6de46fb87f8ed1c21e3bb62c133176
Reviewed-on: https://chromium-review.googlesource.com/225262
Tested-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Shannon Woods <shannonwoods@chromium.org>

tests/angle_tests/ClearTest.cpp

@@ -148,7 +148,9 @@ TYPED_TEST(ClearTestES3, MaskedClearBufferBug)
     // TODO: glReadBuffer support
     glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT1, GL_TEXTURE_2D, 0, 0);
     glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, textures[1], 0);
-    EXPECT_PIXEL_EQ(0, 0, 0, 127, 255, 255);
+
+    //TODO(jmadill): Robust handling of pixel test error ranges
+    EXPECT_PIXEL_NEAR(0, 0, 0, 127, 255, 255, 1);
 
     glDeleteTextures(2, textures);
 }