RFR: 6176679: Application freezes when copying an animated gif image to the system clipboard [v4]

[Rajat Mahajan]

> **Problem:**
> 
> On pressing the Copy button we keep waiting in AWT-EventQueue thread in reconstruct() function as we detect that we have missing information for the animated image since we are copying single frame at a time.
> Due to this infinite wait the application freezes.
> 
> **Proposed Fix:**
> 
> There are conditions in the reconstruct() function that avoid entering the wait() code if we have some error reading the image , etc. So, I added the condition to avoid entering the wait() code if we are copying single frame at a time. This sounded logical to me since if we have incomplete information(single frame) about the animated image we shouldn’t keep waiting, as it leads to infinite wait. 
> After this change I see the GIF image being correctly copied and animated.
> 
> 
> **Testing:**
> 
> Added a test for this (bug6176679.java) and tested locally on my Windows machine and on mach5.

Rajat Mahajan has updated the pull request incrementally with two additional commits since the last revision:

 - code cleanup
 - code cleanup

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/13414/files
  - new: https://git.openjdk.org/jdk/pull/13414/files/c8bd3d99..003eb7ea

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=13414&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=13414&range=02-03

  Stats: 13 lines in 1 file changed: 9 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/13414.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13414/head:pull/13414

PR: https://git.openjdk.org/jdk/pull/13414