Make GL_ANGLE_framebuffer_multisample enableable.

src/libANGLE/Caps.cpp

@@ -650,7 +650,7 @@ const ExtensionInfoMap &GetExtensionInfoMap()
         map["GL_KHR_robust_buffer_access_behavior"] = esOnlyExtension(&Extensions::robustBufferAccessBehavior);
         map["GL_EXT_blend_minmax"] = enableableExtension(&Extensions::blendMinMax);
         map["GL_ANGLE_framebuffer_blit"] = esOnlyExtension(&Extensions::framebufferBlit);
-        map["GL_ANGLE_framebuffer_multisample"] = esOnlyExtension(&Extensions::framebufferMultisample);
+        map["GL_ANGLE_framebuffer_multisample"] = enableableExtension(&Extensions::framebufferMultisample);
         map["GL_ANGLE_instanced_arrays"] = esOnlyExtension(&Extensions::instancedArrays);
         map["GL_ANGLE_pack_reverse_row_order"] = esOnlyExtension(&Extensions::packReverseRowOrder);
         map["GL_OES_standard_derivatives"] = enableableExtension(&Extensions::standardDerivatives);

src/libANGLE/State.cpp

@@ -191,11 +191,8 @@ void State::initialize(const Context *context,
     mDebug.setOutputEnabled(debug);
     mDebug.setMaxLoggedMessages(extensions.maxDebugLoggedMessages);
 
-    if (extensions.framebufferMultisample)
-    {
-        mMultiSampling = true;
-        mSampleAlphaToOne = false;
-    }
+    mMultiSampling    = true;
+    mSampleAlphaToOne = false;
 
     mCoverageModulation = GL_NONE;
 

src/tests/gl_tests/WebGLCompatibilityTest.cpp

@@ -642,6 +642,36 @@ TEST_P(WebGLCompatibilityTest, EnableQueryExtensions)
     }
 }
 
+// Test enabling the GL_ANGLE_framebuffer_multisample extension
+TEST_P(WebGLCompatibilityTest, EnableFramebufferMultisampleExtension)
+{
+    EXPECT_FALSE(extensionEnabled("GL_ANGLE_framebuffer_multisample"));
+
+    // This extensions become core in in ES3/WebGL2.
+    ANGLE_SKIP_TEST_IF(getClientMajorVersion() >= 3);
+
+    GLint maxSamples = 0;
+    glGetIntegerv(GL_MAX_SAMPLES, &maxSamples);
+    EXPECT_GL_ERROR(GL_INVALID_ENUM);
+
+    GLRenderbuffer renderbuffer;
+    glBindRenderbuffer(GL_RENDERBUFFER, renderbuffer);
+    glRenderbufferStorageMultisampleANGLE(GL_RENDERBUFFER, 1, GL_RGBA4, 1, 1);
+    EXPECT_GL_ERROR(GL_INVALID_OPERATION);
+
+    if (extensionRequestable("GL_ANGLE_framebuffer_multisample"))
+    {
+        glRequestExtensionANGLE("GL_ANGLE_framebuffer_multisample");
+        EXPECT_GL_NO_ERROR();
+
+        glGetIntegerv(GL_MAX_SAMPLES, &maxSamples);
+        EXPECT_GL_NO_ERROR();
+
+        glRenderbufferStorageMultisampleANGLE(GL_RENDERBUFFER, maxSamples, GL_RGBA4, 1, 1);
+        EXPECT_GL_NO_ERROR();
+    }
+}
+
 // Verify that the context generates the correct error when the framebuffer attachments are
 // different sizes
 TEST_P(WebGLCompatibilityTest, FramebufferAttachmentSizeMissmatch)