Fix two source map bugs.
1. Mappings for class member functions didn't have names.
2. In cases like "foo.bar" mappings for "bar" point to "foo".
Also added a test covering small variety of JS constructs.
Tested:
unit test
java.lang.RuntimeException: __the_message__!
at com.google.j2cl.junit.integration.stacktrace.data.ThrowsInJsFunction$MyFunctionImpl.run(ThrowsInJsFunction.java:55)
- at apply(blaze-out/k8-fastbuild/bin/third_party/java_src/j2cl/jre/java/jre.js.zip!/javaemul/internal/nativebootstrap/Util.impl.java.js:173:14)
+ at apply(blaze-out/k8-fastbuild/bin/third_party/java_src/j2cl/jre/java/jre.js.zip!/javaemul/internal/nativebootstrap/Util.impl.java.js:173:31)
at com.google.j2cl.junit.integration.stacktrace.data.ThrowsInJsFunction.executesFunction(ThrowsInJsFunction.java:60)
at com.google.j2cl.junit.integration.stacktrace.data.ThrowsInJsFunction$1.run(ThrowsInJsFunction.java:46)
at com.google.j2cl.junit.integration.stacktrace.data.ThrowsInJsFunction.executesFunction(ThrowsInJsFunction.java:60)
