GLES1: Clip plane API and rendering

- Add unit tests for the API
- Update test expectations

+ Pass through point size from the vertex array to the shader,
required for new tests to pass.

BUG=angleproject:2306

Change-Id: Ib19436c1f4cb12873adea94f734c821363f9e27d
Reviewed-on: https://chromium-review.googlesource.com/1079993
Commit-Queue: Lingfeng Yang <lfy@google.com>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
diff --git a/src/libANGLE/Context.cpp b/src/libANGLE/Context.cpp
index e5e9112..27ba206 100644
--- a/src/libANGLE/Context.cpp
+++ b/src/libANGLE/Context.cpp
@@ -1683,6 +1683,9 @@
         case GL_MAX_LIGHTS:
             *params = mCaps.maxLights;
             break;
+        case GL_MAX_CLIP_PLANES:
+            *params = mCaps.maxClipPlanes;
+            break;
         // GLES1 emulation: Vertex attribute queries
         case GL_VERTEX_ARRAY_BUFFER_BINDING:
         case GL_NORMAL_ARRAY_BUFFER_BINDING:
@@ -7064,6 +7067,7 @@
             case GL_MAX_PROJECTION_STACK_DEPTH:
             case GL_MAX_TEXTURE_STACK_DEPTH:
             case GL_MAX_LIGHTS:
+            case GL_MAX_CLIP_PLANES:
             case GL_VERTEX_ARRAY_STRIDE:
             case GL_NORMAL_ARRAY_STRIDE:
             case GL_COLOR_ARRAY_STRIDE: