Added Blink-side support for EXT_blend_minmax WebGL extension

Source/core/html/canvas/WebGLRenderingContextBase.cpp

Index: Source/core/html/canvas/WebGLRenderingContextBase.cpp
diff --git a/Source/core/html/canvas/WebGLRenderingContextBase.cpp b/Source/core/html/canvas/WebGLRenderingContextBase.cpp
index ef1f4ffc64e992cd12231089d55eddcaf98719a1..44257b1cd9224d4839c5782592c8ff55309c4cb9 100644
--- a/Source/core/html/canvas/WebGLRenderingContextBase.cpp
+++ b/Source/core/html/canvas/WebGLRenderingContextBase.cpp
@@ -38,6 +38,7 @@
 #include "core/html/HTMLVideoElement.h"
 #include "core/html/ImageData.h"
 #include "core/html/canvas/ANGLEInstancedArrays.h"
+#include "core/html/canvas/EXTBlendMinMax.h"
 #include "core/html/canvas/EXTFragDepth.h"
 #include "core/html/canvas/EXTShaderTextureLOD.h"
 #include "core/html/canvas/EXTTextureFilterAnisotropic.h"
@@ -5090,6 +5091,12 @@ bool WebGLRenderingContextBase::validateBlendEquation(const char* functionName,
     case GL_FUNC_SUBTRACT:
     case GL_FUNC_REVERSE_SUBTRACT:
         return true;
+    case GL_MIN_EXT:
+    case GL_MAX_EXT:
+        if (extensionEnabled(EXTBlendMinMaxName))
+            return true;
+        synthesizeGLError(GL_INVALID_ENUM, functionName, "invalid mode");
+        return false;
     default:
         synthesizeGLError(GL_INVALID_ENUM, functionName, "invalid mode");
         return false;