Tweaks in how to apply bitmap filter levels in GPU.

src/gpu/SkGpuDevice.cpp

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkGpuDevice.h"
 
 #include "effects/GrBicubicEffect.h"
@@ skipping 1186 matching lines @@
         case SkPaint::kNone_FilterLevel:
             tileFilterPad = 0;
             textureFilterMode = GrTextureParams::kNone_FilterMode;
             break;
         case SkPaint::kLow_FilterLevel:
             tileFilterPad = 1;
             textureFilterMode = GrTextureParams::kBilerp_FilterMode;
             break;
         case SkPaint::kMedium_FilterLevel:
             tileFilterPad = 1;
-            textureFilterMode = GrTextureParams::kMipMap_FilterMode;
+            if (fContext->getMatrix().getMinStretch() < SK_Scalar1) {
+                textureFilterMode = GrTextureParams::kMipMap_FilterMode;
+            } else {
+                // Don't trigger MIP level generation unnecessarily.
+                textureFilterMode = GrTextureParams::kBilerp_FilterMode;
+            }
             break;
-        case SkPaint::kHigh_FilterLevel: {
+        case SkPaint::kHigh_FilterLevel:
             // Minification can look bad with the bicubic effect.
             if (fContext->getMatrix().getMinStretch() >= SK_Scalar1) {
                 // We will install an effect that does the filtering in the shader.
                 textureFilterMode = GrTextureParams::kNone_FilterMode;
                 tileFilterPad = GrBicubicEffect::kFilterTexelPad;
                 doBicubic = true;
             } else {
-                // We don't yet support doing bicubic filtering with an interior clamp. Fall back
-                // to MIPs
                 textureFilterMode = GrTextureParams::kMipMap_FilterMode;
                 tileFilterPad = 1;
             }
             break;
-        }
         default:
             SkErrorInternals::SetError( kInvalidPaint_SkError,
                                         "Sorry, I don't understand the filtering "
                                         "mode you asked for.  Falling back to "
                                         "MIPMaps.");
             tileFilterPad = 1;
             textureFilterMode = GrTextureParams::kMipMap_FilterMode;
             break;
     }
 
@@ skipping 678 matching lines @@
                          GrTexture* texture,
                          bool needClear)
     : SkBitmapDevice(make_bitmap(context, texture->asRenderTarget())) {
 
     SkASSERT(texture && texture->asRenderTarget());
     // This constructor is called from onCreateCompatibleDevice. It has locked the RT in the texture
     // cache. We pass true for the third argument so that it will get unlocked.
     this->initFromRenderTarget(context, texture->asRenderTarget(), true);
     fNeedClear = needClear;
 }