Fix ClearTest.RGB8WithMaskFramebuffer.

src/tests/gl_tests/ClearTest.cpp

@@ -190,12 +190,6 @@ TEST_P(ClearTest, ChangeFramebufferAttachmentFromRGBAtoRGB)
 // Test clearing a RGB8 Framebuffer with a color mask.
 TEST_P(ClearTest, RGB8WithMaskFramebuffer)
 {
-    // TODO(fjhenigman): Diagnose and fix http://anglebug.com/2681
-    ANGLE_SKIP_TEST_IF(IsOzone() && IsOpenGLES());
-
-    // TODO(lucferron): Figure out why this test fails on OSX / OpenGL.
-    // http://anglebug.com/2674
-    ANGLE_SKIP_TEST_IF(IsOSX() && IsDesktopOpenGL());
     glBindFramebuffer(GL_FRAMEBUFFER, mFBOs[0]);
 
     GLTexture texture;
@@ -205,14 +199,21 @@ TEST_P(ClearTest, RGB8WithMaskFramebuffer)
                  GL_UNSIGNED_BYTE, nullptr);
     glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, texture, 0);
 
-    glColorMask(GL_TRUE, GL_TRUE, GL_FALSE, GL_TRUE);
+    glClearColor(0.2f, 0.4f, 0.6f, 0.8f);
+    glClear(GL_COLOR_BUFFER_BIT);
+
+    // Since there's no alpha, we expect to get 255 back instead of the clear value (204).
+    EXPECT_PIXEL_NEAR(0, 0, 51, 102, 153, 255, 1.0);
 
-    // alpha shouldn't really be taken into account and we should find 255 as a result since we
-    // are writing to a RGB8 texture. Also, the
-    glClearColor(0.5f, 0.5f, 0.5f, 0.2f);
+    glColorMask(GL_TRUE, GL_TRUE, GL_FALSE, GL_TRUE);
+    glClearColor(0.1f, 0.3f, 0.5f, 0.7f);
     glClear(GL_COLOR_BUFFER_BIT);
 
-    EXPECT_PIXEL_NEAR(0, 0, 128, 128, 0, 255, 1.0);
+    // The blue channel was masked so its value should be unchanged.
+    EXPECT_PIXEL_NEAR(0, 0, 26, 77, 153, 255, 1.0);
+
+    // Restore default.
+    glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
 }
 
 TEST_P(ClearTest, ClearIssue)