android: add ZoomConstraints (Fennec import)

Change-Id: I7bb840f74675a2e23fd7ee45aad4d48a705e567e
android: remove getViewport and getZoomFactor (Fennec import)

Change-Id: Id28994e51adf779bd5462901c23c488e3465f91b
android: add PanZoomTarget (Fennec import)

Change-Id: Ib946b7a95cd59833a732e3da6c139e848778e1bc
android: move scrollBy & scaleWithFocus to PZC (Fennec Import)

Change-Id: Ie0d23b302994134f9d382e255b0408f7c9f1c1fb
android: remove notifyLayerClientOfGeometryChange (Fennec import)

Change-Id: Ibc1f4d11dcfdf177cd45fcf689b518d975b13709
android: solve black screen on load - call setForceRedraw

Change-Id: Ia9ae05a14c0c751fde961186be350d57d5308519
android: Improve panning smoothness (Fennec import)

Change-Id: I3983709651548eb97e588ebe2c2de608a4a4dfc7
android: replace with ImmutableViewportMetrics (Fennec import)

Change-Id: I46509f8be4dc49dac45eb98059dad25e150988dd
android: revert ScreenshotLayer draw method back

Own draw method expands the picture correctly but for some reason
the SingleTileLayer draw method does not so revert back.

Change-Id: Ie8e39fc46b84ae410439a781928ff79bc1503d10
android: LayerRendered - rename member to mScreenShotLayer

Change-Id: I16fbda06c75bbf80e7d2c2b045418297589c6ff7
android: minimize the rounding error, clean-up MultiTileLayer

Change-Id: Ib167acf5914596b69ee240255aaab173a0570038