Faster Class::FindClassMethod().

Avoid using `strlen()` on ASCII strings from DexFile.
This was a missed opportunity in
    https://android-review.googlesource.com/963405 .

Also optimize iteration over declared methods of a class.
Load the dex file before the loop and avoid the runtime
method check in `ArtMethod::GetMethodNameView()` by using
the `DexFile` interface directly.

Test: m test-art-host-gtest
Test: testrunner.py --host --optimizing
Bug: 181943478
Change-Id: I1ce3659b7f1fbcfc11d52626f9feb9be666d1161
4 files changed