Clean up specifying colors and texture scale in MipmapTest

Remove unnecessary scale parameter from MipmapTestES3, and use the
GLColor class and EXPECT_PIXEL_COLOR_EQ instead of EXPECT_PIXEL_EQ for
greater readability.

BUG=angleproject:596
TEST=angle_end2end_tests

Change-Id: I79c30ce85be5d554d89197f8f1ce7ab0c51c11b6
Reviewed-on: https://chromium-review.googlesource.com/344513
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Olli Etuaho <oetuaho@nvidia.com>
diff --git a/src/tests/test_utils/ANGLETest.h b/src/tests/test_utils/ANGLETest.h
index 0a4108a..9d850a6 100644
--- a/src/tests/test_utils/ANGLETest.h
+++ b/src/tests/test_utils/ANGLETest.h
@@ -58,6 +58,7 @@
     static const GLColor blue;
     static const GLColor cyan;
     static const GLColor black;
+    static const GLColor white;
 };
 
 // Useful to cast any type to GLubyte.
@@ -72,18 +73,6 @@
 std::ostream &operator<<(std::ostream &ostream, const GLColor &color);
 GLColor ReadColor(GLint x, GLint y);
 
-template <typename T>
-void FillWithRGBA(size_t pixelCount, T red, T green, T blue, T alpha, T *outArray)
-{
-    for (size_t i = 0u; i < pixelCount; ++i)
-    {
-        outArray[i * 4u]      = red;
-        outArray[i * 4u + 1u] = green;
-        outArray[i * 4u + 2u] = blue;
-        outArray[i * 4u + 3u] = alpha;
-    }
-}
-
 }  // namespace angle
 
 #define EXPECT_PIXEL_EQ(x, y, r, g, b, a) \