abstract name of clipping ops, to transtion to a more restricted set

SkRegion::Op --> SkCanvas::ClipOp (alias) --> SkClipOp

pre-CL needed in chrome : https://codereview.chromium.org/2355583002/

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2355483002

Review-Url: https://codereview.chromium.org/2355483002
diff --git a/samplecode/SampleApp.cpp b/samplecode/SampleApp.cpp
index ee2b6e3..33b38c0 100644
--- a/samplecode/SampleApp.cpp
+++ b/samplecode/SampleApp.cpp
@@ -1349,7 +1349,7 @@
 
     if (fUseClip) {
         canvas->drawColor(0xFFFF88FF);
-        canvas->clipPath(fClipPath, SkRegion::kIntersect_Op, true);
+        canvas->clipPath(fClipPath, SkCanvas::kIntersect_Op, true);
     }
 
     // Install a flags filter proxy canvas if needed
diff --git a/samplecode/SampleClip.cpp b/samplecode/SampleClip.cpp
index 16390d8..06bd717 100644
--- a/samplecode/SampleClip.cpp
+++ b/samplecode/SampleClip.cpp
@@ -143,7 +143,7 @@
             canvas->save();
             for (size_t i = 0; i < SK_ARRAY_COUNT(gProc); ++i) {
                 canvas->save();
-                canvas->clipPath(clipPath, SkRegion::kIntersect_Op, SkToBool(aa));
+                canvas->clipPath(clipPath, SkCanvas::kIntersect_Op, SkToBool(aa));
 //                canvas->drawColor(SK_ColorWHITE);
                 gProc[i](canvas, SkToBool(aa));
                 canvas->restore();
diff --git a/samplecode/SampleClipDrawMatch.cpp b/samplecode/SampleClipDrawMatch.cpp
index b010ad0..ddb9f66 100644
--- a/samplecode/SampleClipDrawMatch.cpp
+++ b/samplecode/SampleClipDrawMatch.cpp
@@ -164,43 +164,43 @@
 
         switch (fGeom) {
         case kRect_Geometry:
-            canvas->clipRect(create_rect(offset), SkRegion::kReplace_Op, useAA);
+            canvas->clipRect(create_rect(offset), SkCanvas::kReplace_Op, useAA);
             break;
         case kRRect_Geometry:
-            canvas->clipRRect(create_rrect(offset), SkRegion::kReplace_Op, useAA);
+            canvas->clipRRect(create_rrect(offset), SkCanvas::kReplace_Op, useAA);
             break;
         case kCircle_Geometry:
-            canvas->clipRRect(create_circle(offset), SkRegion::kReplace_Op, useAA);
+            canvas->clipRRect(create_circle(offset), SkCanvas::kReplace_Op, useAA);
             break;
         case kConvexPath_Geometry:
-            canvas->clipPath(create_convex_path(offset), SkRegion::kReplace_Op, useAA);
+            canvas->clipPath(create_convex_path(offset), SkCanvas::kReplace_Op, useAA);
             break;
         case kConcavePath_Geometry:
-            canvas->clipPath(create_concave_path(offset), SkRegion::kReplace_Op, useAA);
+            canvas->clipPath(create_concave_path(offset), SkCanvas::kReplace_Op, useAA);
             break;
         case kRectAndRect_Geometry: {
             SkRect r = create_rect(offset);
             r.offset(fSign * kXlate, fSign * kXlate);
-            canvas->clipRect(r, SkRegion::kReplace_Op, true); // AA here forces shader clips
-            canvas->clipRect(create_rect(offset), SkRegion::kIntersect_Op, useAA);
+            canvas->clipRect(r, SkCanvas::kReplace_Op, true); // AA here forces shader clips
+            canvas->clipRect(create_rect(offset), SkCanvas::kIntersect_Op, useAA);
             } break;
         case kRectAndRRect_Geometry: {
             SkRect r = create_rect(offset);
             r.offset(fSign * kXlate, fSign * kXlate);
-            canvas->clipRect(r, SkRegion::kReplace_Op, true); // AA here forces shader clips
-            canvas->clipRRect(create_rrect(offset), SkRegion::kIntersect_Op, useAA);
+            canvas->clipRect(r, SkCanvas::kReplace_Op, true); // AA here forces shader clips
+            canvas->clipRRect(create_rrect(offset), SkCanvas::kIntersect_Op, useAA);
             } break;
         case kRectAndConvex_Geometry: {
             SkRect r = create_rect(offset);
             r.offset(fSign * kXlate, fSign * kXlate);
-            canvas->clipRect(r, SkRegion::kReplace_Op, true); // AA here forces shader clips
-            canvas->clipPath(create_convex_path(offset), SkRegion::kIntersect_Op, useAA);
+            canvas->clipRect(r, SkCanvas::kReplace_Op, true); // AA here forces shader clips
+            canvas->clipPath(create_convex_path(offset), SkCanvas::kIntersect_Op, useAA);
             } break;
         case kRectAndConcave_Geometry: {
             SkRect r = create_rect(offset);
             r.offset(fSign * kXlate, fSign * kXlate);
-            canvas->clipRect(r, SkRegion::kReplace_Op, true); // AA here forces shader clips
-            canvas->clipPath(create_concave_path(offset), SkRegion::kIntersect_Op, useAA);
+            canvas->clipRect(r, SkCanvas::kReplace_Op, true); // AA here forces shader clips
+            canvas->clipPath(create_concave_path(offset), SkCanvas::kIntersect_Op, useAA);
             } break;
         }
 
diff --git a/samplecode/SampleComplexClip.cpp b/samplecode/SampleComplexClip.cpp
index aab759c..7439d91 100644
--- a/samplecode/SampleComplexClip.cpp
+++ b/samplecode/SampleComplexClip.cpp
@@ -79,14 +79,14 @@
         canvas->drawPath(clipB, paint);
 
         static const struct {
-            SkRegion::Op fOp;
-            const char*  fName;
+            SkCanvas::ClipOp fOp;
+            const char*      fName;
         } gOps[] = { //extra spaces in names for measureText
-            {SkRegion::kIntersect_Op,         "Isect "},
-            {SkRegion::kDifference_Op,        "Diff " },
-            {SkRegion::kUnion_Op,             "Union "},
-            {SkRegion::kXOR_Op,               "Xor "  },
-            {SkRegion::kReverseDifference_Op, "RDiff "}
+            {SkCanvas::kIntersect_Op,         "Isect "},
+            {SkCanvas::kDifference_Op,        "Diff " },
+            {SkCanvas::kUnion_Op,             "Union "},
+            {SkCanvas::kXOR_Op,               "Xor "  },
+            {SkCanvas::kReverseDifference_Op, "RDiff "}
         };
 
         canvas->translate(0, SkIntToScalar(40));
diff --git a/samplecode/SampleFatBits.cpp b/samplecode/SampleFatBits.cpp
index a1ef3ad..8da6058 100644
--- a/samplecode/SampleFatBits.cpp
+++ b/samplecode/SampleFatBits.cpp
@@ -258,7 +258,7 @@
         fMinSurface->getCanvas()->save();
         SkRect r = fClipRect;
         r.inset(SK_Scalar1/3, SK_Scalar1/3);
-        fMinSurface->getCanvas()->clipRect(r, SkRegion::kIntersect_Op, true);
+        fMinSurface->getCanvas()->clipRect(r, SkCanvas::kIntersect_Op, true);
     }
     fMinSurface->getCanvas()->drawLine(pts[0].fX, pts[0].fY, pts[1].fX, pts[1].fY, paint);
     if (fUseClip) {
diff --git a/samplecode/SampleIdentityScale.cpp b/samplecode/SampleIdentityScale.cpp
index b6af3ce..8d1bc36 100644
--- a/samplecode/SampleIdentityScale.cpp
+++ b/samplecode/SampleIdentityScale.cpp
@@ -65,7 +65,7 @@
           SkRect r = { 100, 100, 356, 356 };
           SkPath clipPath;
           clipPath.addRoundRect(r, SkIntToScalar(5), SkIntToScalar(5));
-          canvas->clipPath(clipPath, SkRegion::kIntersect_Op, SkToBool(1));
+          canvas->clipPath(clipPath, SkCanvas::kIntersect_Op, SkToBool(1));
           text = "Scaled = 0";
         }
         canvas->drawBitmap( fBM, 100, 100, &paint );
diff --git a/samplecode/SampleLayers.cpp b/samplecode/SampleLayers.cpp
index 4386976..52e6593 100644
--- a/samplecode/SampleLayers.cpp
+++ b/samplecode/SampleLayers.cpp
@@ -255,7 +255,7 @@
         m.postTranslate(fCenter.x(), fCenter.y());
         path.transform(m);
 
-        canvas->clipPath(path, SkRegion::kIntersect_Op, true);
+        canvas->clipPath(path, SkCanvas::kIntersect_Op, true);
         const SkRect bounds = path.getBounds();
 
         SkPaint paint;