Bumping gaia.json for 1 gaia-1_2 revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-1_2/rev/a2308d075e50
Author: Gabriele Svelto <gsvelto@mozilla.com>
Desc: Bug 944242 - Properly handle do-not-track options when upgrading from 1.1 r=kaze
Bug 933483 - Add nsPIDOMWindow::IsCurrentInnerWindow. r=smaug, a=koi+
Bug 933483 - Don't fire events (and especially request animation frame events) when we're in a modal dialog. r=smaug, a=koi+
Bug 944125 - test_bug602962.xul is racy. r=ehsan, a=test-only
Bug 944126 - Random failures with browser_privatebrowsing_aboutSessionRestore.js. r=ehsan, a=test-only
Bug 944128 - Random failures with test_bug_461710_perwindowpb.html. r=ehsan, a=test-only
Bug 949227 - browser_bug609700.js | Found an unexpected tab at the end of test run: about:blank. r=gavin, a=test-only
Bug 546169 - Use an event listener instead of a timeout to avoid intermittent failures. r=gavin, a=test-only
Bug 950337 - Random failures in privatebrowsing/test/browser/browser_privatebrowsing_cache.js. r=ehsan, a=test-only
Bug 948406 - Append some zeros to EGL attrib lists to work around a bug in Android/B2G emulator. r=vladv, a=lsblakk
Bug 949855 - No sound comes out when FM Radio is first time started. r=mchen, a=koi+