Allow ReadPixels with GL_FLOAT type and EXT_color_buffer_half_float.

BUG=angleproject:2148

Change-Id: If3fa4a42a7343ed133f85be1a4d9d0fa48b427cd
Reviewed-on: https://chromium-review.googlesource.com/665158
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Geoff Lang <geofflang@chromium.org>
diff --git a/src/libANGLE/validationES.cpp b/src/libANGLE/validationES.cpp
index 7d19f72..c124406 100644
--- a/src/libANGLE/validationES.cpp
+++ b/src/libANGLE/validationES.cpp
@@ -176,7 +176,8 @@
             return context->getClientVersion() >= ES_3_0;
 
         case GL_FLOAT:
-            return context->getClientVersion() >= ES_3_0 || context->getExtensions().textureFloat;
+            return context->getClientVersion() >= ES_3_0 || context->getExtensions().textureFloat ||
+                   context->getExtensions().colorBufferHalfFloat;
 
         case GL_HALF_FLOAT:
             return context->getClientVersion() >= ES_3_0 ||