Android: Add a build step for validating dex references.

This CL introduces a build step for validating the output produced by
R8 and dexsplitter for static library APKs. The class loaders used
by static libraries cannot access classes located in the main APK, but
R8/dexsplitter may produce dex files that include such illegal
references.

Also included is a new proguard config that avoids illegal dex
references in trichrome_library_apk.

Bug: 956839
Change-Id: I550a90af155a2e88444ae734ea31fadd410f8b9a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1702809
Commit-Queue: Eric Stevenson <[email protected]>
Reviewed-by: Andrew Grieve <[email protected]>
Cr-Commit-Position: refs/heads/master@{#680421}
diff --git a/PRESUBMIT.py b/PRESUBMIT.py
index fe8fb86..007377f 100644
--- a/PRESUBMIT.py
+++ b/PRESUBMIT.py
@@ -1221,6 +1221,7 @@
     'build/android/gyp/merge_manifest.pydeps',
     'build/android/gyp/prepare_resources.pydeps',
     'build/android/gyp/proguard.pydeps',
+    'build/android/gyp/validate_static_library_dex_references.pydeps',
     'build/android/gyp/write_build_config.pydeps',
     'build/android/gyp/write_native_libraries_java.pydeps',
     'build/android/gyp/zip.pydeps',