Infer sampler precision from pixel config

include/gpu/GrCaps.h

Index: include/gpu/GrCaps.h
diff --git a/include/gpu/GrCaps.h b/include/gpu/GrCaps.h
index d698a4142c2b5f783d1753e8678f18b96615b7de..d3faf26c60f02a63a6d37ea47ec0295943dff543 100644
--- a/include/gpu/GrCaps.h
+++ b/include/gpu/GrCaps.h
@@ -76,6 +76,17 @@ public:
     };
 
     /**
+    * Returns the effective amount of precision found in floating point types with a given precision
+    * qualifier.
+    *
+    *  e.g. If lowp == mediump, effectiveFloatPrecision(lowp) is mediump.
+    *       If the platform doesn't use precision, effectiveFloatPrecision() is always highp.
+    */
+    GrSLPrecision effectiveFloatPrecision(GrShaderType shaderType, GrSLPrecision precision) const {
+        return fEffectiveFloatPrecisions[shaderType][precision];
+    }
+
+    /**
     * Is there any difference between the float shader variable precision types? If this is true
     * then unless the shader type is not supported, any call to getFloatShaderPrecisionInfo() would
     * report the same info for all precisions in all shader types.
@@ -101,6 +112,9 @@ public:
     }
 
 protected:
+    /** Subclasses must call this after filling in the shader precision table. */
+    void initEffectiveFloatPrecisionTable();
+
     /** Subclasses must call this after initialization in order to apply caps overrides requested by
         the client. Note that overrides will only reduce the caps never expand them. */
     void applyOptionsOverrides(const GrContextOptions& options);
@@ -114,6 +128,7 @@ protected:
 
     bool fShaderPrecisionVaries;
     PrecisionInfo fFloatPrecisions[kGrShaderTypeCount][kGrSLPrecisionCount];
+    GrSLPrecision fEffectiveFloatPrecisions[kGrShaderTypeCount][kGrSLPrecisionCount];
     int fPixelLocalStorageSize;
     bool fPLSPathRenderingSupport;