Infer sampler precision from pixel config

include/gpu/GrTypesPriv.h

Index: include/gpu/GrTypesPriv.h
diff --git a/include/gpu/GrTypesPriv.h b/include/gpu/GrTypesPriv.h
index 39386f0140a7253fa0289172a5b09cfd4113b23a..0115a6bb2a62a6bb6997eba7b0688bc011d8b794 100644
--- a/include/gpu/GrTypesPriv.h
+++ b/include/gpu/GrTypesPriv.h
@@ -71,6 +71,48 @@ enum GrSLPrecision {
 
 static const int kGrSLPrecisionCount = kLast_GrSLPrecision + 1;
 
+static inline GrSLPrecision GrPixelConfigPrecision(GrPixelConfig config) {
+    static const GrSLPrecision precisions[] = {
+        kLow_GrSLPrecision,       // kUnknown_GrPixelConfig
+        kLow_GrSLPrecision,       // kAlpha_8_GrPixelConfig
+        kLow_GrSLPrecision,       // kIndex_8_GrPixelConfig
+        kLow_GrSLPrecision,       // kRGB_565_GrPixelConfig
+        kLow_GrSLPrecision,       // kRGBA_4444_GrPixelConfig
+        kLow_GrSLPrecision,       // kRGBA_8888_GrPixelConfig
+        kLow_GrSLPrecision,       // kBGRA_8888_GrPixelConfig
+        kLow_GrSLPrecision,       // kSRGBA_8888_GrPixelConfig
+        kLow_GrSLPrecision,       // kSBGRA_8888_GrPixelConfig
+        kLow_GrSLPrecision,       // kETC1_GrPixelConfig
+        kLow_GrSLPrecision,       // kLATC_GrPixelConfig
+        kLow_GrSLPrecision,       // kR11_EAC_GrPixelConfig
+        kLow_GrSLPrecision,       // kASTC_12x12_GrPixelConfig
+        kHigh_GrSLPrecision,      // kRGBA_float_GrPixelConfig
+        kMedium_GrSLPrecision,    // kAlpha_half_GrPixelConfig
+        kMedium_GrSLPrecision,    // kRGBA_half_GrPixelConfig
+    };
+
+    SkASSERT(config >= 0 && config <= kLast_GrPixelConfig);
+    return precisions[config];
+
+    GR_STATIC_ASSERT(0 == kUnknown_GrPixelConfig);
+    GR_STATIC_ASSERT(1 == kAlpha_8_GrPixelConfig);
+    GR_STATIC_ASSERT(2 == kIndex_8_GrPixelConfig);
+    GR_STATIC_ASSERT(3 == kRGB_565_GrPixelConfig);
+    GR_STATIC_ASSERT(4 == kRGBA_4444_GrPixelConfig);
+    GR_STATIC_ASSERT(5 == kRGBA_8888_GrPixelConfig);
+    GR_STATIC_ASSERT(6 == kBGRA_8888_GrPixelConfig);
+    GR_STATIC_ASSERT(7 == kSRGBA_8888_GrPixelConfig);
+    GR_STATIC_ASSERT(8 == kSBGRA_8888_GrPixelConfig);
+    GR_STATIC_ASSERT(9 == kETC1_GrPixelConfig);
+    GR_STATIC_ASSERT(10 == kLATC_GrPixelConfig);
+    GR_STATIC_ASSERT(11 == kR11_EAC_GrPixelConfig);
+    GR_STATIC_ASSERT(12 == kASTC_12x12_GrPixelConfig);
+    GR_STATIC_ASSERT(13 == kRGBA_float_GrPixelConfig);
+    GR_STATIC_ASSERT(14 == kAlpha_half_GrPixelConfig);
+    GR_STATIC_ASSERT(15 == kRGBA_half_GrPixelConfig);
+    GR_STATIC_ASSERT(SK_ARRAY_COUNT(precisions) == kGrPixelConfigCnt);
+}
+
 /**
  * Gets the vector size of the SLType. Returns -1 for void, matrices, and samplers.
  */