Added back initialization of m_scale in PinchViewport
Added back initialization of m_scale in PinchViewport

Fixes uninitialized usage valgrind warnings.

BUG=372226

Review URL: https://codereview.chromium.org/280473002

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@173871 bbb929c8-8fbe-4397-9dbb-9b2b20218538

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