better way to look for method bodies to inline, helps with SI-4767

[magarciaEPFL]

This pull request changes a core aspect of the inliner, thus please be sure to re-check.

At least one aspect definitely needs improvement: the definition of isJDKClass(). Ideas are specially welcome about that.

As well as comments about any material effect on performance ( @gkossakowski comes to mind ).

review by @VladUreche
review by @dragos

[scala-jenkins]

Started jenkins job pr-scala-testsuite-linux-opt at https://scala-webapps.epfl.ch/jenkins/job/pr-scala-testsuite-linux-opt/452/

[scala-jenkins]

jenkins job pr-scala-testsuite-linux-opt: Failed - https://scala-webapps.epfl.ch/jenkins/job/pr-scala-testsuite-linux-opt/452/

[magarciaEPFL]

Let's see if the above was an intermittent failure.
PLS REBUILD ALL

[scala-jenkins]

Started jenkins job pr-scala-testsuite-linux-opt at https://scala-webapps.epfl.ch/jenkins/job/pr-scala-testsuite-linux-opt/454/

[scala-jenkins]

jenkins job pr-scala-testsuite-linux-opt: Failed - https://scala-webapps.epfl.ch/jenkins/job/pr-scala-testsuite-linux-opt/454/

[paulp]

What property exactly is it trying to identify? Here's an implementation which should under normal conditions identify anything which originates in a jar under the running vm. How exactly this will interact with symlinks etc. I don't know.

class JdkClassIdentifier extends (String => Boolean) {
  private val javaHome         = sys.props("java.home")
  private val loader           = new URLClassLoader(Array[URL]())
  // Since I'm not sure of the intent behind the code I'm
  // writing, I don't know whether pre-filtering based on
  // package names is desirable.
  private val knownJdkPackages = "java javax com.sun sun" split ' ' map (_ + ".") toVector

  def apply[T](implicit ctag: reflect.ClassTag[T]): Boolean = apply(ctag.runtimeClass.getName)
  def apply(name: String): Boolean = {
    knownJdkPackages.exists(name startsWith _) || {
      val path = name.replace('.', '/') + ".class"
      loader getResource path match {
        case null => false
        case url  => 
          // At this point it looks something like
          //    jar:file:/Library/Java/JavaVirtualMachines/1.7.0.jdk/Contents/Home/jre/lib/rt.jar!/java/lang/String.class
          // getPath drops "jar:" so we remove "file:" - presumably if there is no jar
          // involved, getPath will drop "file:" instead.
          url.getPath stripPrefix "file:" startsWith javaHome
      }
    }
  }
}

[magarciaEPFL]

Thanks for the discussion, it will help me in fixing the issues uncovered by the build failure.