Add support for READ_BUFFER and SAMPLER_BINDING queries

BUG=angleproject:1101
TEST=dEQP-GLES3.functional.state_query.integers.* (all pass)

Change-Id: I3a70335eeaef39822700ff639443a59849ed53fa
Reviewed-on: https://chromium-review.googlesource.com/329866
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Olli Etuaho <oetuaho@nvidia.com>
diff --git a/src/libANGLE/State.cpp b/src/libANGLE/State.cpp
index abd4558..bee5456 100644
--- a/src/libANGLE/State.cpp
+++ b/src/libANGLE/State.cpp
@@ -1606,6 +1606,13 @@
       case GL_PIXEL_UNPACK_BUFFER_BINDING:
         *params = mUnpack.pixelBuffer.id();
         break;
+      case GL_READ_BUFFER:
+          *params = mReadFramebuffer->getReadBufferState();
+          break;
+      case GL_SAMPLER_BINDING:
+          ASSERT(mActiveSampler < mMaxCombinedTextureImageUnits);
+          *params = getSamplerId(static_cast<GLuint>(mActiveSampler));
+          break;
       case GL_DEBUG_LOGGED_MESSAGES:
           *params = static_cast<GLint>(mDebug.getMessageCount());
           break;