Implementation of 2D canvas context lost/restored events

LayoutTests/fast/canvas/script-tests/canvas-extremely-large-dimensions.js

-description("Series of tests to ensure correct behaviour when canvas size is extremely large.");
-var canvas = document.createElement('canvas')
-var ctx = canvas.getContext('2d');
-
-// WebIDL defines width and height as int. 2147483647 is int max.
-var extremelyLargeNumber = 2147483647;
-canvas.width = extremelyLargeNumber;
-canvas.height = extremelyLargeNumber;
-
-debug("check for crash on extremely large canvas size.");
-useCanvasContext(ctx);
-var imageData = ctx.getImageData(1, 1, 98, 98);
-var imgdata = imageData.data;
-// Blink returns zero color if the image buffer does not exist.
-shouldBe("imgdata[4]", "0");
-shouldBe("imgdata[5]", "0");
-shouldBe("imgdata[6]", "0");
-
-debug("check for crash after resetting to the same size.");
-canvas.width = extremelyLargeNumber;
-useCanvasContext(ctx);
-imageData = ctx.getImageData(1, 1, 98, 98);
-imgdata = imageData.data;
-shouldBe("imgdata[4]", "0");
-shouldBe("imgdata[5]", "0");
-shouldBe("imgdata[6]", "0");
-
-// googol is parsed to 0.
-var googol = Math.pow(10, 100);
-debug("check for crash after resizing to googol.");
-canvas.width = googol;
-canvas.height = googol;
-useCanvasContext(ctx);
-imageData = ctx.getImageData(1, 1, 98, 98);
-imgdata = imageData.data;
-shouldBe("imgdata[4]", "0");
-shouldBe("imgdata[5]", "0");
-shouldBe("imgdata[6]", "0");
-
-debug("check for crash after resetting to the same size.");
-canvas.width = googol;
-useCanvasContext(ctx);
-imageData = ctx.getImageData(1, 1, 98, 98);
-imgdata = imageData.data;
-shouldBe("imgdata[4]", "0");
-shouldBe("imgdata[5]", "0");
-shouldBe("imgdata[6]", "0");
-
-debug("check again for crash on extremely large canvas size.");
-canvas.width = extremelyLargeNumber;
-canvas.height = extremelyLargeNumber;
-useCanvasContext(ctx);
-imageData = ctx.getImageData(1, 1, 98, 98);
-imgdata = imageData.data;
-shouldBe("imgdata[4]", "0");
-shouldBe("imgdata[5]", "0");
-shouldBe("imgdata[6]", "0");
-
-function useCanvasContext(ctx) {
-    ctx.fillStyle = 'green';
-    ctx.fillRect(0, 0, 100, 100);
-    for(var i = 0; i < 100; i++) {
-        // This API tries to create an image buffer if the image buffer is not created.
-        ctx.getImageData(1, 1, 1, 1);
-    }
-    ctx.beginPath();
-    ctx.rect(0,0,100,100);
-    ctx.save();
-    ctx.fillStyle = 'red';
-    ctx.fillRect(0, 0, 100, 100);
-    ctx.restore();
-    ctx.fillStyle = 'green';
-    ctx.fill();
-}
-
-debug("after resizing to normal size, the canvas must be in a valid state.");
-canvas.width = 100;
-canvas.height = 100;
-ctx.fillStyle = 'blue';
-ctx.fillRect(0, 0, 100, 100);
-imageData = ctx.getImageData(1, 1, 98, 98);
-imgdata = imageData.data;
-shouldBe("imgdata[4]", "0");
-shouldBe("imgdata[5]", "0");
-shouldBe("imgdata[6]", "255");