separate out the scaline-choosing to simplify chooseProcs

BUG=skia:
TBR=

Review URL: https://codereview.chromium.org/796063007
diff --git a/src/core/SkBitmapProcState.cpp b/src/core/SkBitmapProcState.cpp
index ab38b6b..ada974a 100644
--- a/src/core/SkBitmapProcState.cpp
+++ b/src/core/SkBitmapProcState.cpp
@@ -457,9 +457,11 @@
         }
     }
 
-    // At this point, we know exactly what kind of sampling the per-scanline
-    // shader will perform.
+    return this->chooseScanlineProcs(trivialMatrix, clampClamp, paint);
+}
 
+bool SkBitmapProcState::chooseScanlineProcs(bool trivialMatrix, bool clampClamp,
+                                            const SkPaint& paint) {
     fMatrixProc = this->chooseMatrixProc(trivialMatrix);
     // TODO(dominikg): SkASSERT(fMatrixProc) instead? chooseMatrixProc never returns NULL.
     if (NULL == fMatrixProc) {
@@ -518,7 +520,7 @@
                 return false;
         }
 
-    #if !SK_ARM_NEON_IS_ALWAYS
+#if !SK_ARM_NEON_IS_ALWAYS
         static const SampleProc32 gSkBitmapProcStateSample32[] = {
             S32_opaque_D32_nofilter_DXDY,
             S32_alpha_D32_nofilter_DXDY,
@@ -588,7 +590,7 @@
             // Don't support A8 -> 565
             NULL, NULL, NULL, NULL
         };
-    #endif
+#endif
 
         fSampleProc32 = SK_ARM_NEON_WRAP(gSkBitmapProcStateSample32)[index];
         index >>= 1;    // shift away any opaque/alpha distinction
@@ -612,10 +614,10 @@
             fShaderProc32 = this->chooseShaderProc32();
         }
     }
-
+    
     // see if our platform has any accelerated overrides
     this->platformProcs();
-
+    
     return true;
 }
 
diff --git a/src/core/SkBitmapProcState.h b/src/core/SkBitmapProcState.h
index add5bf4..fa934dc 100644
--- a/src/core/SkBitmapProcState.h
+++ b/src/core/SkBitmapProcState.h
@@ -135,6 +135,7 @@
 
     MatrixProc chooseMatrixProc(bool trivial_matrix);
     bool chooseProcs(const SkMatrix& inv, const SkPaint&);
+    bool chooseScanlineProcs(bool trivialMatrix, bool clampClamp, const SkPaint& paint);
     ShaderProc32 chooseShaderProc32();
 
     // returns false if we did not try to scale the image. In that case, we