A number of classes used in PolyGerrit are defined in vanilla JS files
that are included multiple times by various elements. For example,
gr-diff-line.js is included by the gr-diff-builder and by gr-diff
elements. Adds #ifndef-style guards to each of these libraries to
prevent redefinition and avoid different elements potentially referring
to different versions of the same class.
Change-Id: I45e3ba425a59989b328475b1fe58fd9f350c8ae0
This reverts commit 56689af0f92ce13f90ff9369544c5f9cc0412f09.
Reason for revert: This change broke adding draft comments in the diff
view.
Change-Id: Icfbd3eb4e24cce3e1690e7eaf12e14e5705c7e3e
