Use assumevalues instead of assumenosideffects for proguard.

This seems to have the same meaning, however use of "return" in assumenosideffects is not working for some versions of proguard.

Change-Id: Ie6dde7612d25c7ee5fd2d2fd42dfe74444188c41
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1804064Reviewed-by: Sam Maier <smaier@chromium.org>
Reviewed-by: Andrew Grieve <agrieve@chromium.org>
Commit-Queue: Eric Roman <eroman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#696911}

base/android/proguard/chromium_code.flags

@@ -50,9 +50,12 @@
 -assumenosideeffects class ** {
   # Remove @RemovableInRelease methods so long as return values are unused.
   @org.chromium.base.annotations.RemovableInRelease <methods>;
+}
+
+-assumevalues class ** {
   # Remove object @RemovableInRelease methods even when return value is used.
-  # Note: * in return type does not match primitives.
-  @org.chromium.base.annotations.RemovableInRelease * *(...) return null;
+  # Note: ** in return type does not match primitives.
+  @org.chromium.base.annotations.RemovableInRelease ** *(...) return null;
   # Remove boolean @RemovableInRelease methods even when return value is used.
   @org.chromium.base.annotations.RemovableInRelease boolean *(...) return false;
 }

chrome/android/java/monochrome_public_bundle.proguard_flags.expected

@@ -226,9 +226,12 @@
 -assumenosideeffects class ** {
   # Remove @RemovableInRelease methods so long as return values are unused.
   @org.chromium.base.annotations.RemovableInRelease <methods>;
+}
+
+-assumevalues class ** {
   # Remove object @RemovableInRelease methods even when return value is used.
-  # Note: * in return type does not match primitives.
-  @org.chromium.base.annotations.RemovableInRelease * *(...) return null;
+  # Note: ** in return type does not match primitives.
+  @org.chromium.base.annotations.RemovableInRelease ** *(...) return null;
   # Remove boolean @RemovableInRelease methods even when return value is used.
   @org.chromium.base.annotations.RemovableInRelease boolean *(...) return false;
 }