android: Remove the ability to load multiple library in custom linkers.

This was unused since at least 2016 (see crbug.com/657093). Remove the code to
support this both in LegacyLinker and ModernLinker. In the process, further
unify the two linkers, and refactor state tracking.

Bug: 979638

Change-Id: I4fad98228a841e1959a93f8ef5dbe5d29dfe7f30
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1715485Reviewed-by: Yaron Friedman <yfriedman@chromium.org>
Reviewed-by: Andrew Grieve <agrieve@chromium.org>
Reviewed-by: Egor Pasko <pasko@chromium.org>
Commit-Queue: Benoit L <lizeb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#683155}

base/android/linker/modern_linker_jni.cc

@@ -420,22 +420,6 @@ bool LoadNoSharedRelocations(const String& path) {
 
 }  // namespace
 
-// Get the CPU ABI string for which the linker is running.
-//
-// The returned string is used to construct the path to libchrome.so when
-// loading directly from APK.
-//
-// |env| is the current JNI environment handle.
-// |clazz| is the static class handle for org.chromium.base.Linker,
-// and is ignored here.
-// Returns the CPU ABI string for which the linker is running.
-JNI_GENERATOR_EXPORT jstring
-Java_org_chromium_base_library_1loader_ModernLinker_nativeGetCpuAbi(
-    JNIEnv* env,
-    jclass clazz) {
-  return env->NewStringUTF(CURRENT_ABI);
-}
-
 JNI_GENERATOR_EXPORT jboolean
 Java_org_chromium_base_library_1loader_ModernLinker_nativeLoadLibraryCreateRelros(
     JNIEnv* env,

content/public/android/java/src/org/chromium/content/app/ContentChildProcessServiceDelegate.java

@@ -83,9 +83,7 @@ public class ContentChildProcessServiceDelegate implements ChildProcessServiceDe
 
         if (LibraryLoader.useChromiumLinker() && !LibraryLoader.getInstance().isLoadedByZygote()) {
             Bundle sharedRelros = connectionBundle.getBundle(Linker.EXTRA_LINKER_SHARED_RELROS);
-            if (sharedRelros != null) {
-                getLinker().useSharedRelros(sharedRelros);
-            }
+            if (sharedRelros != null) getLinker().provideSharedRelros(sharedRelros);
         }
     }