Update locked_region_code_injection tool to ASM 6.0-BETA.

ASM 6 is required to read version 53 (OpenJDK 9) class files.

Test: make EXPERIMENTAL_USE_OPENJDK9=true services.core
      (in the presence of other unsubmitted CLs that fix
      other issues)
Test: Copied all required dependencies into a subdirectory lib/,
      then ran the steps from TestMain.java, both for OpenJDK 8
      and OpenJDK 9 toolchains.
Bug: 67676752

Change-Id: If324d8ea28450d9a8426a2279190b2f4d9213ed5