D3D11: Implement dirty bits for texture updates.

BUG=angleproject:1387

Change-Id: I5f759c3dc60b53a5d4f8a1dd1f4a1d3d5330bfda
Reviewed-on: https://chromium-review.googlesource.com/648487
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
diff --git a/src/libANGLE/renderer/d3d/ProgramD3D.cpp b/src/libANGLE/renderer/d3d/ProgramD3D.cpp
index b41df35..0b00f65 100644
--- a/src/libANGLE/renderer/d3d/ProgramD3D.cpp
+++ b/src/libANGLE/renderer/d3d/ProgramD3D.cpp
@@ -706,11 +706,11 @@
     }
 }
 
-void ProgramD3D::updateSamplerMapping()
+ProgramD3D::SamplerMapping ProgramD3D::updateSamplerMapping()
 {
     if (!mDirtySamplerMapping)
     {
-        return;
+        return SamplerMapping::WasClean;
     }
 
     mDirtySamplerMapping = false;
@@ -771,6 +771,8 @@
             }
         }
     }
+
+    return SamplerMapping::WasDirty;
 }
 
 gl::LinkResult ProgramD3D::load(const gl::Context *context,