Use Canvas#drawParagraph

We'll eventually remove Paragraph#paint.

Fixes #2694

examples/layers/raw/hello_world.dart

@@ -22,7 +22,7 @@ void beginFrame(Duration timeStamp) {
   final ui.PictureRecorder recorder = new ui.PictureRecorder();
   final ui.Canvas canvas = new ui.Canvas(recorder, physicalBounds);
   canvas.scale(devicePixelRatio, devicePixelRatio);
-  paragraph.paint(canvas, new ui.Offset(
+  canvas.drawParagraph(paragraph, new ui.Offset(
     (logicalSize.width - paragraph.maxIntrinsicWidth) / 2.0,
     (logicalSize.height - paragraph.height) / 2.0
   ));

examples/layers/raw/text.dart

@@ -21,7 +21,7 @@ ui.Picture paint(ui.Rect paintBounds) {
 
   // The paint method of Pargraph draws the contents of the paragraph unto the
   // given canvas.
-  paragraph.paint(canvas, new ui.Offset(paragraph.maxWidth / -2.0, (paragraph.maxWidth / 2.0) - 125));
+  canvas.drawParagraph(paragraph, new ui.Offset(paragraph.maxWidth / -2.0, (paragraph.maxWidth / 2.0) - 125));
 
   return recorder.endRecording();
 }

packages/flutter/lib/src/painting/text_painter.dart

@@ -294,7 +294,7 @@ class TextPainter {
   /// Paints the text onto the given canvas at the given offset.
   void paint(Canvas canvas, Offset offset) {
     assert(!_needsLayout && "Please call layout() before paint() to position the text before painting it." is String);
-    _paragraph.paint(canvas, offset);
+    canvas.drawParagraph(_paragraph, offset);
   }
 
   Offset _getOffsetFromUpstream(int offset, Rect caretPrototype) {

packages/flutter/lib/src/rendering/error.dart

@@ -113,7 +113,7 @@ class RenderErrorBox extends RenderBox {
           _paragraph.maxWidth = size.width;
         }
         _paragraph.layout();
-        _paragraph.paint(context.canvas, offset);
+        context.canvas.drawParagraph(_paragraph, offset);
       }
     } catch (e) { }
   }