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Revision 4e5f09f89e6f1976dd49a57ba46cd447c7e19a1e authored by Alex Moshchuk on 13 April 2018, 15:22:14 UTC, committed by Chromium WPT Sync on 13 April 2018, 15:22:14 UTC 
Reland: Use PostTask to schedule cross-process postMessage forwarding.
 
Changes from original attempt at https://crrev.com/c/999182:
- fix flakiness in two additional ChromeOS login tests
- fix CSP WPT tests to not depend on ordering between iframe's onload
  and postMessage - see https://crbug.com/832319.

Previously, we sent the IPC to forward a cross-process postMessage
immediately.  This caused a behavioral difference from the
same-process case where the postMessage is always scheduled.  Namely,
in a scenario like this:

  frame.postMessage(...);
  doSomethingThatSendsIPCsToFrame(frame);

the IPCs from JS following the postMessage would've been ordered
incorrectly, causing |frame| to see their side effects after the
postMessage dispatch in the cross-process case, whereas they would be
seen before the postMessage dispatch in the same-process case.  One
example of this is frame.focus(), and another is a frame element
onload event (dispatched via FrameHostMsg_DispatchLoad) arriving after
a postMessage dispatched from an inline script while the frame was
still loading.

To resolve these ordering concerns, this CL changes cross-process
postMessage to do a PostTask on the sender side before sending the
message to the browser process.  This improves the current state of
the world, but does not yet achieve a perfect match for the IPC
ordering in the same-process case - see discussion on the bug.

Bug: 828529
Change-Id: I62a627c501526d09900be4f5bd2c899acf4d1e07
Reviewed-on: https://chromium-review.googlesource.com/999182
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Commit-Queue: Alex Moshchuk <alexmos@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#550284}
Reviewed-on: https://chromium-review.googlesource.com/1011287
Cr-Commit-Position: refs/heads/master@{#550621}
1 parent f90d3d6
Raw File
first-contentful-canvas.html 
<!DOCTYPE html>
<head>
<title>Performance Paint Timing Test: FCP due to canvas</title>
</head>
<body>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<canvas id="canvas" width="200" height="200" ></canvas>

<script>
async_test(function (t) {
    const canvas = document.getElementById("canvas");
    const context = canvas.getContext("2d");
    context.beginPath();
    context.moveTo(0,0);
    context.lineTo(300,150);
    context.stroke();
    function testPaintEntries() {
        const bufferedEntries = performance.getEntriesByType('paint');
        if (bufferedEntries.length < 2) {
            t.step_timeout(function() {
                testPaintEntries();
            }, 20);
            return;
        }
        t.step(function() {
            assert_equals(bufferedEntries.length, 2, "There should be two paint timing instances.");
            assert_equals(bufferedEntries[0].entryType, "paint");
            assert_equals(bufferedEntries[0].name, "first-paint");
            assert_equals(bufferedEntries[1].entryType, "paint");
            assert_equals(bufferedEntries[1].name, "first-contentful-paint");
            t.done();
        });
    };
    t.step(function() {
        testPaintEntries();
    });
}, "First contentful paint fires due to canvas render.");
</script>
</body>
</html>
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