Fix flaky browser.test_sdl_mouse in Chrome. (#24237)

In small windows the spinner, progress bar, and status text shift around
causing the canvas below them to be at a different location from when
the test starts.

I've filed #24236 about better ways to fix this. For now, this seems
like the smallest change.

Author: brendandahl

.circleci/config.yml

@@ -316,7 +316,8 @@ commands:
             # --no-sandbox because we are running as root and chrome requires
             # this flag for now: https://crbug.com/638180
             CHROME_FLAGS_BASE: "--no-first-run -start-maximized --no-sandbox --use-gl=swiftshader --user-data-dir=/tmp/chrome-emscripten-profile --enable-experimental-web-platform-features"
-            CHROME_FLAGS_HEADLESS: "--headless=new --remote-debugging-port=1234"
+            # Increase the window size to avoid flaky sdl tests see #24236.
+            CHROME_FLAGS_HEADLESS: "--headless=new --window-size=1024,768 --remote-debugging-port=1234"
             CHROME_FLAGS_WASM: "--enable-experimental-webassembly-features --js-flags=\"--experimental-wasm-stack-switching --experimental-wasm-type-reflection\""
             CHROME_FLAGS_NOCACHE: "--disk-cache-dir=/dev/null --disk-cache-size=1 --media-cache-size=1 --disable-application-cache --incognito"
             # The runners lack sound hardware so fallback to a dummy device (and