Merge pull request #9213 from samjoch/follow-up-bug-823414

Bug 823414 - B2G browser gradient value does not match the gradient found in Settings (followup) r=me(cherry picked from commit 208848fd6dd04c090df3b89c0a1a51282c4731f7)

Conflicts:
	apps/browser/style/images/drawer-header-background.png
	apps/browser/style/images/drawer-header-background@2x.png
	apps/browser/style/images/tabs-badge-background@2x.png
	apps/browser/style/images/tabs-list-background@2x.png