Conditionally insert gl_PointSize into shaders.

BUG=chromium:648816
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2358843002

Review-Url: https://codereview.chromium.org/2358843002
diff --git a/src/gpu/glsl/GrGLSLVertexShaderBuilder.cpp b/src/gpu/glsl/GrGLSLVertexShaderBuilder.cpp
index 4931e0f..f8302b3 100644
--- a/src/gpu/glsl/GrGLSLVertexShaderBuilder.cpp
+++ b/src/gpu/glsl/GrGLSLVertexShaderBuilder.cpp
@@ -46,8 +46,10 @@
                           posVar.c_str(), fRtAdjustName, fRtAdjustName);
     }
     // We could have the GrGeometryProcessor do this, but its just easier to have it performed
-    // here. If we ever need to set variable pointsize, then we can reinvestigate
-    this->codeAppend("gl_PointSize = 1.0;");
+    // here. If we ever need to set variable pointsize, then we can reinvestigate.
+    if (this->getProgramBuilder()->desc().header().fHasPointSize) {
+        this->codeAppend("gl_PointSize = 1.0;");
+    }
 }
 
 void GrGLSLVertexBuilder::onFinalize() {