RFR: JDK-8297414: Remove easy warnings in javafx.controls [v6]

[John Hendrikx]

> Note: I ran into a `javac` compiler bug while replacing types with diamond operators (ecj has no issues).  I had two options, add a `SuppressWarnings("unused")` or to use a lambda instead of a method reference to make `javac` happy.  I choose the later and added a comment so it can be fixed once the bug is fixed.  I've reported the issue here: https://bugs.openjdk.org/browse/JDK-8297428
> 
> - Remove unsupported/unnecessary SuppressWarning annotations
> - Remove reduntant type specifications (use diamond operator)
> - Remove unused or duplicate imports
> - Remove unnecessary casts (type is already correct type or can be autoboxed)
> - Remove unnecessary semi-colons (at end of class definitions, or just repeated ones)
> - Remove redundant super interfaces (interface that is already inherited)
> - Remove unused type parameters
> - Remove declared checked exceptions that are never thrown
> - Add missing `@Override` annotations

John Hendrikx has updated the pull request incrementally with one additional commit since the last revision:

  Replace StubToolkit casts with asserts (2)

-------------

Changes:
  - all: https://git.openjdk.org/jfx/pull/959/files
  - new: https://git.openjdk.org/jfx/pull/959/files/76acacb8..a07f8982

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jfx&pr=959&range=05
 - incr: https://webrevs.openjdk.org/?repo=jfx&pr=959&range=04-05

  Stats: 19 lines in 4 files changed: 13 ins; 1 del; 5 mod
  Patch: https://git.openjdk.org/jfx/pull/959.diff
  Fetch: git fetch https://git.openjdk.org/jfx pull/959/head:pull/959

PR: https://git.openjdk.org/jfx/pull/959