Adding a canvas-specific cache for style-dependent font resolution

This change adds a cache very similar to the one added in
https://src.chromium.org/viewvc/blink?view=rev&revision=198618
The difference is that this cache is specifically for canvases
that are attached to the DOM. These canvases have font resolution
logic that depends on the style of the canvas element. Therefore,
the cache has to be element-specific rather than global to the
document.

BUG=497864

Review URL: https://codereview.chromium.org/1234503007

git-svn-id: svn://svn.chromium.org/blink/trunk@199230 bbb929c8-8fbe-4397-9dbb-9b2b20218538

1 files changed, 6 insertions, 0 deletions

diff --git a/third_party/WebKit/LayoutTests/fast/canvas/canvas-set-font-with-updated-style.html b/third_party/WebKit/LayoutTests/fast/canvas/canvas-set-font-with-updated-style.html
index a6b90fa..9290f32 100644
--- a/third_party/WebKit/LayoutTests/fast/canvas/canvas-set-font-with-updated-style.html
+++ b/third_party/WebKit/LayoutTests/fast/canvas/canvas-set-font-with-updated-style.html
@@ -13,6 +13,12 @@ function drawCanvasText(id, text)
 {
     var canvasElement = document.getElementById(id);
     var context = canvasElement.getContext('2d');
+
+    // Pre-draw pass to add the font to the font cache. This way, the test also
+    // verifies that the style change correctly invalidates the font resolution cache.
+    context.font = '1em Calibri';
+    context.fillText(text, 0, 100);
+
     canvasElement.style.fontSize = '64px';
     context.font = '1em Calibri';
     context.fillText(text, 0, 100);