optimize intersect, use getType to utilize fast-case in preTranslate

10-15% speed up in clip_record_overhead bench

Comparing the raw fType field was missing the (maybe deprecatable) IsRectToRect
bit (0x10), which is set for identity and translate matrices, so we were
never taking the fast case.

BUG=skia:

Change-Id: I1c73f4bae42f2311454c7568ef8891239c3cae83
Reviewed-on: https://skia-review.googlesource.com/9388
Commit-Queue: Mike Reed <reed@google.com>
Reviewed-by: Herb Derby <herb@google.com>
diff --git a/src/core/SkRasterClip.cpp b/src/core/SkRasterClip.cpp
index f43d14e..6f9eb6b 100644
--- a/src/core/SkRasterClip.cpp
+++ b/src/core/SkRasterClip.cpp
@@ -115,6 +115,15 @@
 }
 
 void SkConservativeClip::op(const SkIRect& devRect, SkRegion::Op op) {
+    if (SkRegion::kIntersect_Op == op) {
+        if (devRect.isEmpty()) {
+            fBounds.setEmpty();
+        } else {
+            (void)fBounds.intersect(devRect);
+        }
+        return;
+    }
+
     // This may still create a complex region (which we would then take the bounds
     // Perhaps we should inline the op-logic directly to never create the rgn...
     SkRegion result;