Move GrInvariantOutput out of GrProcessor and into its own class.

This will help with the ability to subclass, add to, etc. GrInvariantOutput. Also it was simply
getting a little too big to be a "supporting" subclass
BUG=skia:

Review URL: https://codereview.chromium.org/699943003
diff --git a/src/gpu/effects/GrDistanceFieldTextureEffect.h b/src/gpu/effects/GrDistanceFieldTextureEffect.h
index ea02d19..bcc4088 100644
--- a/src/gpu/effects/GrDistanceFieldTextureEffect.h
+++ b/src/gpu/effects/GrDistanceFieldTextureEffect.h
@@ -14,6 +14,7 @@
 class GrGLDistanceFieldTextureEffect;
 class GrGLDistanceFieldNoGammaTextureEffect;
 class GrGLDistanceFieldLCDTextureEffect;
+class GrInvariantOutput;
 
 enum GrDistanceFieldEffectFlags {
     kSimilarity_DistanceFieldEffectFlag = 0x01,   // ctm is similarity matrix
@@ -80,7 +81,7 @@
 
     virtual bool onIsEqual(const GrGeometryProcessor& other) const SK_OVERRIDE;
 
-    virtual void onComputeInvariantOutput(InvariantOutput* inout) const SK_OVERRIDE;
+    virtual void onComputeInvariantOutput(GrInvariantOutput* inout) const SK_OVERRIDE;
 
     GrTextureAccess    fTextureAccess;
 #ifdef SK_GAMMA_APPLY_TO_A8
@@ -126,7 +127,7 @@
 
     virtual bool onIsEqual(const GrGeometryProcessor& other) const SK_OVERRIDE;
 
-    virtual void onComputeInvariantOutput(InvariantOutput* inout) const SK_OVERRIDE;
+    virtual void onComputeInvariantOutput(GrInvariantOutput* inout) const SK_OVERRIDE;
 
     GrTextureAccess    fTextureAccess;
     uint32_t           fFlags;
@@ -172,7 +173,7 @@
 
     virtual bool onIsEqual(const GrGeometryProcessor& other) const SK_OVERRIDE;
 
-    virtual void onComputeInvariantOutput(InvariantOutput* inout) const SK_OVERRIDE;
+    virtual void onComputeInvariantOutput(GrInvariantOutput* inout) const SK_OVERRIDE;
 
     GrTextureAccess    fTextureAccess;
     GrTextureAccess    fGammaTextureAccess;