Reland "Reland "Revert "Use OpenGL sampler objects when available."""

This reverts commit bfb3df4.

Reason for revert: <INSERT REASONING HERE>

Original change's description:
> Revert "Reland "Revert "Use OpenGL sampler objects when available."""
> 
> This reverts commit bffe4ed.
> 
> Reason for revert: <INSERT REASONING HERE>
> 
> Original change's description:
> > Reland "Revert "Use OpenGL sampler objects when available.""
> >
> > This reverts commit d46987b.
> >
> > Reason for revert: breaking asan bot in chrome roll
> >
> > Original change's description:
> > > Revert "Revert "Use OpenGL sampler objects when available.""
> > >
> > > Put setting GL min/max texture lod behind caps check.
> > >
> > > Bug: skia:8471
> > >
> > >
> > > This reverts commit 1bccae5.
> > >
> > > Change-Id: I8b98df6578a678bbb8b283d8203621a992be4ede
> > > Reviewed-on: https://skia-review.googlesource.com/c/163782
> > > Reviewed-by: Brian Salomon <bsalomon@google.com>
> > > Commit-Queue: Brian Salomon <bsalomon@google.com>
> >
> > TBR=bsalomon@google.com
> >
> > Change-Id: I8e3a0daea12659721d95967ef94c87f856e21948
> > No-Presubmit: true
> > No-Tree-Checks: true
> > No-Try: true
> > Bug: skia:8471
> > Reviewed-on: https://skia-review.googlesource.com/c/163887
> > Reviewed-by: Greg Daniel <egdaniel@google.com>
> > Commit-Queue: Greg Daniel <egdaniel@google.com>
> 
> TBR=egdaniel@google.com,bsalomon@google.com
> 
> Change-Id: Ia35bb7ad13527ffbd04173b517f7399e4a486ff1
> Bug: skia:8471
> Reviewed-on: https://skia-review.googlesource.com/c/163891
> Commit-Queue: Brian Salomon <bsalomon@google.com>
> Reviewed-by: Greg Daniel <egdaniel@google.com>

TBR=egdaniel@google.com,bsalomon@google.com

Change-Id: Ie49071bef7f7c20f0b116cd3a7abfda84728de12
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: skia:8471
Reviewed-on: https://skia-review.googlesource.com/c/164241
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>

include/gpu/GrTypes.h

@@ -238,7 +238,6 @@ enum GrSurfaceOrigin {
  */
 enum GrGLBackendState {
     kRenderTarget_GrGLBackendState     = 1 << 0,
-    // Also includes samplers bound to texture units.
     kTextureBinding_GrGLBackendState   = 1 << 1,
     // View state stands for scissor and viewport
     kView_GrGLBackendState             = 1 << 2,

src/gpu/GrSwizzle.h

@@ -52,11 +52,6 @@ class GrSwizzle {
     /** 4 char null terminated string consisting only of chars 'r', 'g', 'b', 'a'. */
     const char* c_str() const { return fSwiz; }
 
-    char operator[](int i) const {
-        SkASSERT(i >= 0 && i < 4);
-        return fSwiz[i];
-    }
-
     /** Applies this swizzle to the input color and returns the swizzled color. */
     GrColor applyTo(GrColor color) const {
         int idx;
@@ -121,7 +116,7 @@ class GrSwizzle {
             case GrColor_SHIFT_G : return 'g';
             case GrColor_SHIFT_B : return 'b';
             case GrColor_SHIFT_A : return 'a';
-            default:               return -1;
+            default:  return -1;
         }
     }
 

src/gpu/gl/GrGLCreateNullInterface.cpp

@@ -419,10 +419,6 @@ class NullInterface : public GrGLTestInterface {
         SK_ABORT("Not implemented");
     }
 
-    GrGLvoid genSamplers(GrGLsizei n, GrGLuint* samplers) override {
-        this->genGenericIds(n, samplers);
-    }
-
     GrGLvoid genTextures(GrGLsizei n, GrGLuint *textures) override {
         this->genGenericIds(n, textures);
     }