script: A couple mutation observer fixes.
I felt like doing Servo stuff while trying to catch Gecko intermittents :)
This fixes most of #21233. I haven't dug into the other test.
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Track hash changes in session history
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Adds tracking of hash changes in the session history.
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Add some support for WPT tests in an Android emulator through WebDriver
This succeeds on my machine:
`./mach test-wpt --product servodriver --binary etc/run_in_headless_android_emulator.py --binary-arg servo-x86 --binary-arg target/i686-linux-android/release/servo.apk /_mozilla/mozilla/DOMParser.html`
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```
0:27.48 pid:4157 Traceback (most recent call last):
0:27.48 pid:4157 File "/home/simon/servo1/etc/run_in_headless_android_emulator.py", line 212, in <module>
0:27.48 pid:4157 sys.exit(main(*sys.argv[1:]))
0:27.48 pid:4157 File "/home/simon/servo1/etc/run_in_headless_android_emulator.py", line 72, in main
0:27.48 pid:4157 forward_webdriver(adb, args)
0:27.48 pid:4157 File "/home/simon/servo1/etc/run_in_headless_android_emulator.py", line 163, in forward_webdriver
0:27.48 pid:4157 ports = [int(part) for part in split if part]
0:27.48 pid:4157 ValueError: invalid literal for int() with base 10: 'None'
```
```
Traceback (most recent call last):
File "/home/simon/servo1/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/testrunner.py", line 90, in run
rv = commands[command](*args)
File "/home/simon/servo1/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/testrunner.py", line 110, in wait
self.executor.wait()
File "/home/simon/servo1/tests/wpt/web-platform-tests/tools/wptrunner/wptrunner/executors/base.py", line 209, in wait
self.protocol.base.wait()
AttributeError: 'ServoWebDriverProtocol' object has no attribute 'base'
```
Implement update source set & select image source
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- [x] These changes fix#11416 (github issue number if applicable).
- [x] These changes require tests but cannot be written until implementation of responsive images is complete
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Make fetch() API use same-origin credentials by default
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fix block size for absolute replaced element
Absolutely replaced elements with padding were incorrectly setting their
block size to include twice the padding values. This attempts to stop
that extra padding for replaced elements but leave the working flow for
non replaced elements
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