Add control of manual mipmapping to GrContextOptions

include/gpu/GrContextOptions.h

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrContextOptions_DEFINED
 #define GrContextOptions_DEFINED
 
 #include "SkTypes.h"
 
 struct GrContextOptions {
     GrContextOptions()
         : fSuppressPrints(false)
         , fMaxTextureSizeOverride(SK_MaxS32)
         , fMaxTileSizeOverride(0)
         , fSuppressDualSourceBlending(false)
         , fBufferMapThreshold(-1)
         , fUseDrawInsteadOfPartialRenderTargetWrite(false)
         , fImmediateMode(false)
         , fClipBatchToBounds(false)
         , fDrawBatchBounds(false)
         , fMaxBatchLookback(-1)
         , fMaxBatchLookahead(-1)
-        , fUseShaderSwizzling(false) {}
+        , fUseShaderSwizzling(false)
+        , fDoManualMipmapping(false) {}
 
     // Suppress prints for the GrContext.
     bool fSuppressPrints;
 
     /** Overrides: These options override feature detection using backend API queries. These
         overrides can only reduce the feature set or limits, never increase them beyond the
         detected values. */
 
     int  fMaxTextureSizeOverride;
     /** If non-zero, overrides the maximum size of a tile for sw-backed images and bitmaps rendered
@@ skipping 23 matching lines @@
     bool fDrawBatchBounds;
 
     /** For debugging, override the default maximum look-back or look-ahead window for GrBatch
         combining. */
     int fMaxBatchLookback;
     int fMaxBatchLookahead;
 
     /** Force us to do all swizzling manually in the shader and don't rely on extensions to do
         swizzling. */
     bool fUseShaderSwizzling;
+
+    /** Construct mipmaps manually, via repeated downsampling draw-calls. This is used when
+        the driver's implementation (glGenerateMipmap) contains bugs. This requires mipmap
+        level and LOD control (ie desktop or ES3). */
+    bool fDoManualMipmapping;
 };
 
 #endif