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This CL fixes an issue with the initial app sync on sign-in causing many
taskbar flashes due to icon creation always sending a SHChangeNotify.

This shouldn't be necessary for icon creation due to shortcut creation so
avoid SHChangeNotify in this case.

BUG=470002

Review URL: https://codereview.chromium.org/1026113003

Cr-Commit-Position: refs/heads/master@{#322324}