Modify release_beta to modify experiment files (testing3 and testing_changes3) so it's easy to roll changes out gradually to the population

Fix a crash on 10.9 and earlier when tabs don't have close buttons and the titles are long. Issue 4985

Change how orphan tab fillers are found in contentInRange:. An out-of-bounds lookup in eolBlock: was removed (tabFillerOrphansOnRow:line+1, when line is the last line). This should speed up the method by not creating lots of index sets and searching the line twice (except when there are lots of tab filler orphans, which is rare).

Extend contentInRange:... to support truncating the head of its result instead of always truncating the tail when cappedAtSize>=0. This fixes a bug where prefixes for semantic history got their tails truncated when ignoring hard newlines (or if the session is over 2000 cells wide). Issue 4902.

Fix a bug where the alt grid's state wasn't saved properly for window state restoration (the primary grid's state was saved in its place). Issue 5000

Do not setClientSize: when width or height is negative, which can apparently happen when a monitor is unplugged. Issue 1722 comment by dillonhaferon 7/21

Trim trailing newline and adjacent whitespace when selecting the output of the last command. Issue 4975

- Set the showTitle flag in a tab's session viws when creating a tmux tab. This fixes a bug where there would be unused space at the bottom of a fullscreen window because -recompact would throw out the extra room left for the title bar.

Fix a bug where a fullscreen window with a horizontal split with cycle between two different sizes (issue 4933):

- Make addSplitter:toIntervalMap:forHeight:origin: use the size of the scrollview, not the size of the session view. If there is a per-pane titlebar it shouldn't be counted since the height is used to compute the number of rows.

- Get rid of maxTmuxSize, which double-counted the difference between the root splitter and the flexible view that contained it (tmuxSize already took that into account).

- Make tmuxSize use the floor of the charsDiff values. That's better behaved for negative values, since tmuxSize is meant to be equal to or smaller than the size that would fit on the screen.

Finally, make replaceViewHierarchyWithParseTree: set the showTitle flag. This is mostly on general principal.

Pressing esc in a search field without text should pass the command up to the chain. This allows a window to close. Issue 4970.

Fix horribly broken logic for excluding windows from the popup in the edit key action window. Issue 4968.

Fix a bug where trying to seek instant replay to a nonexistant timestamp caused us to seek to the beginning. Issue 4943

Correct the frame (if the width is not divisble by cell size then the window would change size when exiting DVR) and presence of a session view titlebar when going back in time. Issue 4930

Center tab labels as though there is no close button. If the label is so long that it would overlap the close button, left align it just after the close button. Issue 4915.

When arranging windows horizontally, wait for all windows to exit fullscreen first. This requires queuing up toggle fullscreen operations, so the iTermFullScreenWindowManager got revamped to handle this.