Fix type of RTFlip uniform.

This uniform uses a float2 type, not half2. Previously, this was only a
latent problem, since we treated halfs and floats the same when setting
up uniform buffers.

Change-Id: I54f7033561542cf984c08070b2c3eca4173ca69c
Bug: skia:12339
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/465216
Commit-Queue: John Stiles <johnstiles@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
diff --git a/src/gpu/glsl/GrGLSLProgramBuilder.cpp b/src/gpu/glsl/GrGLSLProgramBuilder.cpp
index 04f54a6..486e04f 100644
--- a/src/gpu/glsl/GrGLSLProgramBuilder.cpp
+++ b/src/gpu/glsl/GrGLSLProgramBuilder.cpp
@@ -471,7 +471,7 @@
     fUniformHandles.fRTFlipUni =
             uniformHandler->internalAddUniformArray(nullptr,
                                                     kFragment_GrShaderFlag,
-                                                    kHalf2_GrSLType,
+                                                    kFloat2_GrSLType,
                                                     name,
                                                     false,
                                                     0,