In convexity checker don't advance last vector when x-product isn't significant.

tests/PathTest.cpp

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkCanvas.h"
 #include "SkPaint.h"
 #include "SkParse.h"
@@ skipping 1133 matching lines @@
 
     SkPath dent;
     dent.moveTo(0, 0);
     dent.lineTo(100*SK_Scalar1, 100*SK_Scalar1);
     dent.lineTo(0, 100*SK_Scalar1);
     dent.lineTo(-50*SK_Scalar1, 200*SK_Scalar1);
     dent.lineTo(-200*SK_Scalar1, 100*SK_Scalar1);
     dent.close();
     check_convexity(reporter, dent, SkPath::kConcave_Convexity);
     check_direction(reporter, dent, SkPath::kCW_Direction);
+
+    // http://skbug.com/2235
+    SkPath strokedSin;
+    for (int i = 0; i < 2000; i++) {
+        SkScalar x = SkIntToScalar(i) / 2;
+        SkScalar y = 500 - (x + SkScalarSin(x / 100) * 40) / 3;
+        if (0 == i) {
+            strokedSin.moveTo(x, y);
+        } else {
+            strokedSin.lineTo(x, y);
+        }
+    }
+    SkStrokeRec stroke(SkStrokeRec::kFill_InitStyle);
+    stroke.setStrokeStyle(2 * SK_Scalar1);
+    stroke.applyToPath(&strokedSin, strokedSin);
+    check_convexity(reporter, strokedSin, SkPath::kConcave_Convexity);
+    check_direction(reporter, strokedSin, kDontCheckDir);
 }
 
 static void check_convex_bounds(skiatest::Reporter* reporter, const SkPath& p,
                                 const SkRect& bounds) {
     REPORTER_ASSERT(reporter, p.isConvex());
     REPORTER_ASSERT(reporter, p.getBounds() == bounds);
 
     SkPath p2(p);
     REPORTER_ASSERT(reporter, p2.isConvex());
     REPORTER_ASSERT(reporter, p2.getBounds() == bounds);
@@ skipping 2326 matching lines @@
     test_addPathMode(reporter, true, true);
     test_extendClosedPath(reporter);
     test_addEmptyPath(reporter, SkPath::kExtend_AddPathMode);
     test_addEmptyPath(reporter, SkPath::kAppend_AddPathMode);
     test_conicTo_special_case(reporter);
     test_get_point(reporter);
     test_contains(reporter);
     PathTest_Private::TestPathTo(reporter);
     PathRefTest_Private::TestPathRef(reporter);
 }