Compute exact bounds for SVGPathElement::getBBox()

The current implementation relies on SkPath::getBounds(), which
computes a conservative result (includes control points).

Use SkPathOps::TightBounds() instead, for an exact answer.

BUG=230599
R=fs@opera.com,pdr@chromium.org,schenney@chromium.org,caryclark@google.com

Review-Url: https://codereview.chromium.org/2168133002
Cr-Commit-Position: refs/heads/master@{#407268}

third_party/WebKit/LayoutTests/svg/custom/getBBox-path-expected.txt

-100 50 FAIL
+100 37.5 PASS

third_party/WebKit/Source/core/svg/SVGPathElement.cpp

@@ -207,4 +207,12 @@ void SVGPathElement::removedFrom(ContainerNode* rootParent)
     invalidateMPathDependencies();
 }
 
+FloatRect SVGPathElement::getBBox()
+{
+    document().updateStyleAndLayoutIgnorePendingStylesheets();
+
+    // We want the exact bounds.
+    return SVGPathElement::asPath().boundingRect(Path::BoundsType::Exact);
+}
+
 } // namespace blink

third_party/WebKit/Source/core/svg/SVGPathElement.h

@@ -50,6 +50,8 @@ public:
     bool isPresentationAttribute(const QualifiedName&) const override;
     bool isPresentationAttributeWithSVGDOM(const QualifiedName&) const override;
 
+    FloatRect getBBox() override;
+
     DECLARE_VIRTUAL_TRACE();
 
 private:

third_party/WebKit/Source/platform/graphics/Path.cpp

@@ -115,14 +115,31 @@ bool Path::strokeContains(const FloatPoint& point, const StrokeData& strokeData)
     return strokePath(strokeData).contains(WebCoreFloatToSkScalar(point.x()), WebCoreFloatToSkScalar(point.y()));
 }
 
-FloatRect Path::boundingRect() const
+namespace {
+
+FloatRect pathBounds(const SkPath& path, Path::BoundsType boundsType)
+{
+    SkRect bounds;
+    if (boundsType == Path::BoundsType::Conservative
+        || !TightBounds(path, &bounds)
+        || bounds.isEmpty()) // workaround for https://bugs.chromium.org/p/skia/issues/detail?id=5555
+        return path.getBounds();
+
+    DCHECK_EQ(boundsType, Path::BoundsType::Exact);
+    return bounds;
+}
+
+} // anonymous ns
+
+// TODO(fmalita): evaluate returning exact bounds in all cases.
+FloatRect Path::boundingRect(BoundsType boundsType) const
 {
-    return m_path.getBounds();
+    return pathBounds(m_path, boundsType);
 }
 
-FloatRect Path::strokeBoundingRect(const StrokeData& strokeData) const
+FloatRect Path::strokeBoundingRect(const StrokeData& strokeData, BoundsType boundsType) const
 {
-    return strokePath(strokeData).getBounds();
+    return pathBounds(strokePath(strokeData), boundsType);
 }
 
 static FloatPoint* convertPathPoints(FloatPoint dst[], const SkPoint src[], int count)

third_party/WebKit/Source/platform/graphics/Path.h

@@ -78,8 +78,13 @@ public:
     bool contains(const FloatPoint&) const;
     bool contains(const FloatPoint&, WindRule) const;
     bool strokeContains(const FloatPoint&, const StrokeData&) const;
-    FloatRect boundingRect() const;
-    FloatRect strokeBoundingRect(const StrokeData&) const;
+
+    enum class BoundsType {
+        Conservative, // Fast version, includes control points.
+        Exact, // Tight, slower version.
+    };
+    FloatRect boundingRect(BoundsType = BoundsType::Conservative) const;
+    FloatRect strokeBoundingRect(const StrokeData&, BoundsType = BoundsType::Conservative) const;
 
     float length() const;
     FloatPoint pointAtLength(float length) const;