Sorry in advance for not knowing the precise terminology:

To gather performance metrics, my workflow involves building a "snapshot" of a local branch, and saving that snapshot for later use. Later, I run all tests from those snapshots sequentially.

Problem: After building and remapping an isolated browser_tests build to another directory, further builds in the original src directory cause the remapped isolated browser_tests to start failing.


    git checkout A
    gclient sync
    gn gen out_linux/Release
    ninja -C out_linux/Release browser_tests
    echo gn > out_linux/Release/mb_type
    ./tools/mb/mb.py isolate //out_linux/Release browser_tests
    ./tools/swarming_client/isolate.py remap -s \
        out_linux/Release/browser_tests.isolated -o ../A-snapshot

    # Success: "../A-snapshot/out_linux/Release/browser_tests \
    #     --gtest_filter=DownloadsBrowserTest.*" succeeds here.

    git checkout B
    ninja -C out_linux/Release browser_tests

    # Failure: The timestamp of ../A-snapshot/out_linux/Release/resources.pak
    # has been mysteriously updated. What did that?
    # "../A-snapshot/out_linux/Release/browser_tests \
    #     --gtest_filter=DownloadsBrowserTest.*" fails.


What magic is happening here, and is there an easier way to create isolated snapshots for later execution without copying the entire src directory?