Make appending default precision be controled by GLSL

src/gpu/glsl/GrGLSL.h

Index: src/gpu/glsl/GrGLSL.h
diff --git a/src/gpu/glsl/GrGLSL.h b/src/gpu/glsl/GrGLSL.h
index 87b3d2daa4afba9801c7b5fcc0b4202276ed296b..a39f104fab0e8d993b88063241f22394c0776942 100644
--- a/src/gpu/glsl/GrGLSL.h
+++ b/src/gpu/glsl/GrGLSL.h
@@ -11,6 +11,8 @@
 #include "GrTypesPriv.h"
 #include "SkString.h"
 
+class GrGLSLCaps;
+
 // Limited set of GLSL versions we build shaders for. Caller should round
 // down the GLSL version to one of these enums.
 enum GrGLSLGeneration {
@@ -56,6 +58,13 @@ inline const char* GrGLSLTexture2DFunctionName(GrSLType coordType, GrGLSLGenerat
 }
 
 /**
+ * Adds a line of GLSL code to declare the default precision for float types.
+ */
+void GrGLSLAppendDefaultFloatPrecisionDeclaration(GrSLPrecision,
+                                                  const GrGLSLCaps& glslCaps,
+                                                  SkString* out);
+
+/**
  * Converts a GrSLType to a string containing the name of the equivalent GLSL type.
  */
 static inline const char* GrGLSLTypeString(GrSLType t) {