Support CHROMIUM_path_rendering fragment operations

This brings two new APIs, BindFragmentInputLocation and
ProgramPathFragmentInputGen that together dictate how the
fragment shader varyings are used.

BUG=angleproject:1382

Change-Id: I4b52fd8a3555235a73aecd4f3dba2d500789cbb0
Reviewed-on: https://chromium-review.googlesource.com/357071
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Sami Väisänen <svaisanen@nvidia.com>
Commit-Queue: Sami Väisänen <svaisanen@nvidia.com>
diff --git a/src/libANGLE/renderer/vulkan/ProgramVk.cpp b/src/libANGLE/renderer/vulkan/ProgramVk.cpp
index e2b3a70..591cf06 100644
--- a/src/libANGLE/renderer/vulkan/ProgramVk.cpp
+++ b/src/libANGLE/renderer/vulkan/ProgramVk.cpp
@@ -201,4 +201,12 @@
     return bool();
 }
 
+void ProgramVk::setPathFragmentInputGen(const std::string &inputName,
+                                        GLenum genMode,
+                                        GLint components,
+                                        const GLfloat *coeffs)
+{
+    UNIMPLEMENTED();
+}
+
 }  // namespace rx