Kill PageSet.AddPage and its remaining usage in: * tools/perf/(benchmarks|measurements)/ * content/test/gpu
Kill PageSet.AddPage and its remaining usage in:
* tools/perf/(benchmarks|measurements)/
* content/test/gpu

BUG=439512

Review URL: https://codereview.chromium.org/800863003

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#308424}

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