--- a/content/canvas/src/WebGLContextGL.cpp
+++ b/content/canvas/src/WebGLContextGL.cpp
@@ -59,16 +59,21 @@
 #if defined(USE_ANGLE)
 // shader translator
 #include "angle/ShaderLang.h"
 #endif
 
 #include "WebGLTexelConversions.h"
 #include "WebGLValidateStrings.h"
 
+// needed to check if current OS is lower than 10.7
+#if defined(MOZ_WIDGET_COCOA)
+#include "nsCocoaFeatures.h"
+#endif
+
 using namespace mozilla;
 
 static bool BaseTypeAndSizeFromUniformType(WebGLenum uType, WebGLenum *baseType, WebGLint *unitSize);
 static WebGLenum InternalFormatForFormatAndType(WebGLenum format, WebGLenum type, bool isGLES2);
 
 /* Helper macros for when we're just wrapping a gl method, so that
  * we can avoid having to type this 500 times.  Note that these MUST
  * NOT BE USED if we need to check any of the parameters.
@@ -4412,22 +4417,16 @@ WebGLContext::Viewport(WebGLint x, WebGL
     if (width < 0 || height < 0)
         return ErrorInvalidValue("Viewport: negative size");
 
     MakeContextCurrent();
     gl->fViewport(x, y, width, height);
     return NS_OK;
 }
 
-#ifdef XP_MACOSX
-#define WEBGL_OS_IS_MAC 1
-#else
-#define WEBGL_OS_IS_MAC 0
-#endif
-
 NS_IMETHODIMP
 WebGLContext::CompileShader(nsIWebGLShader *sobj)
 {
     if (mContextLost)
         return NS_OK;
 
     WebGLShader *shader;
     WebGLuint shadername;
@@ -4475,19 +4474,21 @@ WebGLContext::CompileShader(nsIWebGLShad
         const PRUint32 maxSourceLength = (PRUint32(1)<<18) - 1;
         if (sourceCString.Length() > maxSourceLength)
             return ErrorInvalidValue("compileShader: source has more than %d characters", maxSourceLength);
 
         const char *s = sourceCString.get();
         
         int compileOptions = SH_OBJECT_CODE;
         
+#ifdef XP_MACOSX
         // work around bug 665578
-        if (WEBGL_OS_IS_MAC && gl->Vendor() == gl::GLContext::VendorATI)
+        if (!nsCocoaFeatures::OnLionOrLater() && gl->Vendor() == gl::GLContext::VendorATI)
             compileOptions |= SH_EMULATE_BUILT_IN_FUNCTIONS;
+#endif
 
         if (!ShCompile(compiler, &s, 1, compileOptions)) {
             int len = 0;
             ShGetInfo(compiler, SH_INFO_LOG_LENGTH, &len);
 
             if (len) {
                 nsCAutoString info;
                 info.SetLength(len);