Fix string deduplication for multi-image extensions.

(cherry picked from commit f4ba904ec0ec5e6cefa79c4f598dc0a29b7d4143)

Test: WITH_TIDY=1 m
Test: m test-art-host-gtest
Test: testrunner.py --host --optimizing
Test: aosp_taimen-userdebug boots.
Bug: 153104371
Bug: 152037801
Merged-In: Ib91e7a13047d7da78deb855a6713a1a5d9044463
Change-Id: I57a18de8ce8db728a90c321cbe42a2edc6f1fe4b
1 file changed