Move variations prefs into the variations component

These prefs are used by variations code that is targeted for componentization.

BUG=382865
TBR=thakis

Review URL: https://codereview.chromium.org/1265423003

Cr-Commit-Position: refs/heads/master@{#343661}
void MasterPreferences::InitializeProductFlags() {
  multi_install_ = false;
  chrome_ = true;

  GetBool(installer::master_preferences::kMultiInstall, &multi_install_);

  if (multi_install_) {
    if (!GetBool(installer::master_preferences::kChrome, &chrome_))
      chrome_ = false;
  } else {
    chrome_ = true;
  }
}

void MasterPreferences::InitializeProductFlags() {
  multi_install_ = false;
  chrome_ = true;

  GetBool(installer::master_preferences::kMultiInstall, &multi_install_);

  if (multi_install_) {
    if (!GetBool(installer::master_preferences::kChrome, &chrome_))
      chrome_ = false;
  } else {
    chrome_ = true;
  }
}
