Use GetWidenedBounds in D2D backend.

According to http://stackoverflow.com/questions/32611798, "
Geometry.Bounds (in WPF) is equivalent to
ID2D1Geometry::GetWidenedBounds(0.0f)." so use that. This seems to fix
the problem with D2D reporting an invalid size for
Line/PolylineGeometry, so removed the workaround from there.

src/Perspex.SceneGraph/Media/EllipseGeometry.cs

@@ -49,9 +49,6 @@ namespace Perspex.Media
             PlatformImpl = impl;
         }
 
-        /// <inheritdoc/>
-        public override Rect Bounds => PlatformImpl.Bounds;
-
         /// <inheritdoc/>
         public override Geometry Clone()
         {

src/Perspex.SceneGraph/Media/Geometry.cs

@@ -31,10 +31,7 @@ namespace Perspex.Media
         /// <summary>
         /// Gets the geometry's bounding rectangle.
         /// </summary>
-        public abstract Rect Bounds
-        {
-            get;
-        }
+        public Rect Bounds => PlatformImpl.Bounds;
 
         /// <summary>
         /// Gets the platform-specific implementation of the geometry.

src/Perspex.SceneGraph/Media/LineGeometry.cs

@@ -35,37 +35,6 @@ namespace Perspex.Media
             PlatformImpl = impl;
         }
 
-        /// <inheritdoc/>
-        public override Rect Bounds
-        {
-            get
-            {
-                double xMin, yMin, xMax, yMax;
-                if (_startPoint.X <= _endPoint.X)
-                {
-                    xMin = _startPoint.X;
-                    xMax = _endPoint.X;
-                }
-                else
-                {
-                    xMin = _endPoint.X;
-                    xMax = _startPoint.X;
-                }
-                if (_startPoint.Y <= _endPoint.Y)
-                {
-                    yMin = _startPoint.Y;
-                    yMax = _endPoint.Y;
-                }
-                else
-                {
-                    yMin = _endPoint.Y;
-                    yMax = _startPoint.Y;
-                }
-
-                return new Rect(xMin, yMin, xMax - xMin, yMax - yMin);
-            }
-        }
-
         /// <inheritdoc/>
         public override Geometry Clone()
         {

src/Perspex.SceneGraph/Media/PolylineGeometry.cs

@@ -41,38 +41,6 @@ namespace Perspex.Media
             PlatformImpl = impl;
         }
 
-        /// <inheritdoc/>
-        public override Rect Bounds
-        {
-            get
-            {
-                double xMin = double.MaxValue, yMin = double.MaxValue;
-                double xMax = double.MinValue, yMax = double.MinValue;
-                foreach (var point in _points)
-                {
-                    if (point.X < xMin)
-                    {
-                        xMin = point.X;
-                    }
-                    else if (point.X > xMax)
-                    {
-                        xMax = point.X;
-                    }
-
-                    if (point.Y < yMin)
-                    {
-                        yMin = point.Y;
-                    }
-                    else if (point.Y > yMax)
-                    {
-                        yMax = point.Y;
-                    }
-                }
-
-                return new Rect(xMin, yMin, xMax - xMin, yMax - yMin);
-            }
-        }
-
         /// <inheritdoc/>
         public override Geometry Clone()
         {

src/Perspex.SceneGraph/Media/RectangleGeometry.cs

@@ -31,9 +31,6 @@ namespace Perspex.Media
             PlatformImpl = impl;
         }
 
-        /// <inheritdoc/>
-        public override Rect Bounds => PlatformImpl.Bounds;
-
         /// <inheritdoc/>
         public override Geometry Clone()
         {

src/Perspex.SceneGraph/Media/StreamGeometry.cs

@@ -28,9 +28,6 @@ namespace Perspex.Media
             PlatformImpl = impl;
         }
 
-        /// <inheritdoc/>
-        public override Rect Bounds => PlatformImpl.Bounds;
-
         /// <summary>
         /// Creates a <see cref="StreamGeometry"/> from a string.
         /// </summary>

src/Windows/Perspex.Direct2D1/Media/StreamGeometryImpl.cs

@@ -34,7 +34,7 @@ namespace Perspex.Direct2D1.Media
         }
 
         /// <inheritdoc/>
-        public override Rect Bounds => _path.GetBounds().ToPerspex();
+        public override Rect Bounds => _path.GetWidenedBounds(0).ToPerspex();
 
         /// <inheritdoc/>
         public override D2DGeometry DefiningGeometry => _path;