Fix ASSERT not covering full range of drawbuffer counts.

BUG=angle:841

Change-Id: I59cc281e4848572010cbba3d45382a98063e8db2
Reviewed-on: https://chromium-review.googlesource.com/233210
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Tested-by: Geoff Lang <geofflang@chromium.org>
diff --git a/src/libANGLE/Framebuffer.cpp b/src/libANGLE/Framebuffer.cpp
index e790973..32a2fda 100644
--- a/src/libANGLE/Framebuffer.cpp
+++ b/src/libANGLE/Framebuffer.cpp
@@ -268,7 +268,7 @@
 
 void Framebuffer::setDrawBuffers(size_t count, const GLenum *buffers)
 {
-    ASSERT(count < ArraySize(mDrawBufferStates));
+    ASSERT(count <= ArraySize(mDrawBufferStates));
     std::copy(buffers, buffers + count, mDrawBufferStates);
     std::fill(mDrawBufferStates + count, mDrawBufferStates + ArraySize(mDrawBufferStates), GL_NONE);
 }