Program: Sampler uniform query in front-end.

We have this information stored in the front-end sampler bindings.
This solves sampler uniform query across the various back-ends.

Turns on a bunch of uniform_api dEQP tests.

Bug: angleproject:2612
Change-Id: If8752a26438595ad103598369df360e2f5e12d53
Reviewed-on: https://chromium-review.googlesource.com/1101572
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Luc Ferron <lucferron@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
diff --git a/src/libANGLE/renderer/vulkan/ProgramVk.cpp b/src/libANGLE/renderer/vulkan/ProgramVk.cpp
index a462dba..23fd105 100644
--- a/src/libANGLE/renderer/vulkan/ProgramVk.cpp
+++ b/src/libANGLE/renderer/vulkan/ProgramVk.cpp
@@ -512,11 +512,7 @@
     const gl::VariableLocation &locationInfo = mState.getUniformLocations()[location];
     const gl::LinkedUniform &linkedUniform   = mState.getUniforms()[locationInfo.index];
 
-    if (linkedUniform.isSampler())
-    {
-        UNIMPLEMENTED();
-        return;
-    }
+    ASSERT(!linkedUniform.isSampler());
 
     const gl::ShaderType shaderType = linkedUniform.getFirstShaderTypeWhereActive();
     ASSERT(shaderType != gl::ShaderType::InvalidEnum);