Reorder GL implementations on Mac to not use EGL so early.

Since https://chromium-review.googlesource.com/c/chromium/src/+/1005017/ EGL is
enabled on Mac but not used by default.  The disable_es3_gl_context workaround
removes the kGLImplementationDesktopGLCoreProfile GL implementation from the
list of allowed implementations which now defaults to using EGL when the
intention is that it falls back to a non-core desktop GL profile. Reorder the
implementations so that the fallback happens as expected.

BUG=918365

Change-Id: Ibf9ae089897f32508dd83fed41cfdc8412e9c7bb
Reviewed-on: https://chromium-review.googlesource.com/c/1437060Reviewed-by: Zhenyao Mo <zmo@chromium.org>
Commit-Queue: Geoff Lang <geofflang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#626096}

ui/gl/init/gl_factory_mac.cc

@@ -63,12 +63,12 @@ class NoOpGLSurface : public GLSurface {
 std::vector<GLImplementation> GetAllowedGLImplementations() {
   std::vector<GLImplementation> impls;
   impls.push_back(kGLImplementationDesktopGLCoreProfile);
+  impls.push_back(kGLImplementationDesktopGL);
+  impls.push_back(kGLImplementationAppleGL);
 #if BUILDFLAG(USE_EGL_ON_MAC)
   impls.push_back(kGLImplementationEGLGLES2);
   impls.push_back(kGLImplementationSwiftShaderGL);
 #endif  // BUILDFLAG(USE_EGL_ON_MAC)
-  impls.push_back(kGLImplementationDesktopGL);
-  impls.push_back(kGLImplementationAppleGL);
   return impls;
 }