Merge pull request #855 from nnnick/fix/reset-canvas

Restore original canvas context when destroying

src/Chart.Core.js

@@ -868,6 +868,21 @@
 		destroy : function(){
 			this.clear();
 			unbindEvents(this, this.events);
+			var canvas = this.chart.canvas;
+
+			// Reset canvas height/width attributes starts a fresh with the canvas context
+			canvas.width = this.chart.width;
+			canvas.height = this.chart.height;
+
+			// < IE9 doesn't support removeProperty
+			if (canvas.style.removeProperty) {
+				canvas.style.removeProperty('width');
+				canvas.style.removeProperty('height');
+			} else {
+				canvas.style.removeAttribute('width');
+				canvas.style.removeAttribute('height');
+			}
+
 			delete Chart.instances[this.id];
 		},
 		showTooltip : function(ChartElements, forceRedraw){