8.0-controls-scrum-h138: up to 30% regression in Controls.TreeViewExpand benchmarks

Inline style changes integrated into build 8.0-controls-scrum-h138 results in
up to 30% regression in Controls.TreeViewExpand benchmarks.

Here are the results on Win7-High-Range machine:
 Controls.TreeView-Expand.items100-depth: -20%, 210 fps => 167 fps
 Controls.TreeView-Expand.items100-wide: -27%, 421 fps => 308 fps


I can see in JPA profiles that impl_processCSS time has been increased.
In particular the time spent in StyleHelper.transitionToState has been increased from 3 secs to 7 secs.
The total run time was 30 secs.

Steps to run the benchmark:
> cd JFX_WS/tests/performance/Controls/
> ant
> java -Djavafx.animation.fullspeed=true
    -cp "JFX_HOME/rt/lib/jfxrt.jar;./dist/Controls.jar;../FXBenchmark/dist/FXBenchmark.jar;../../../import/benchmarks-2.1.1/benchmarks-2.1.1.jar"
    jrockit.bm.Main controls.bm.TreeViewExpandBenchmark -i 1 -wt 0 -tr 60 -type depth -size 1000


The full list of changes integrated into 8.0-controls-scrum-h138 is:
    1. branch merge
    2. RT-26554: if an inline style changes, clear the style cache so new styles will be recalculated.
    3. Fixed RT-23878: -fx-ellipsis-string doesn't apply after setStyle