Re-re-land sksl fragment processor support

This reverts commit 5ce397205528f82084fc650c2ce27d246c01da33.

Bug: skia:
Change-Id: I88260c90004610a1cf8ad1a87c2b4b222525bbb6
Reviewed-on: https://skia-review.googlesource.com/21108
Reviewed-by: Ben Wagner <benjaminwagner@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
diff --git a/tests/SkSLGLSLTest.cpp b/tests/SkSLGLSLTest.cpp
index a4a3c0e..8f09d6b 100644
--- a/tests/SkSLGLSLTest.cpp
+++ b/tests/SkSLGLSLTest.cpp
@@ -487,7 +487,8 @@
          "void main() { sk_FragColor.r = 1; }",
          *SkSL::ShaderCapsFactory::ShaderDerivativeExtensionString(),
          "#version 400\n"
-         "out vec4 sk_FragColor;\n"
+         "precision highp float;\n"
+         "out mediump vec4 sk_FragColor;\n"
          "void main() {\n"
          "    sk_FragColor.x = 1.0;\n"
          "}\n");
@@ -496,7 +497,8 @@
          *SkSL::ShaderCapsFactory::ShaderDerivativeExtensionString(),
          "#version 400\n"
          "#extension GL_OES_standard_derivatives : require\n"
-         "out vec4 sk_FragColor;\n"
+         "precision highp float;\n"
+         "out mediump vec4 sk_FragColor;\n"
          "void main() {\n"
          "    sk_FragColor.x = dFdx(1.0);\n"
          "}\n");