[lldb] Refactor the Symbolicator initializer

[JDevlieghere]

Summary

We found out that we have clients relying on the old signature of the Symbolicator initializer. Make the signature compatible again and provide a factory method to initialize the class correctly based on whether you have a target or want the symbolicator to create one for you.

[jingham]

LGTM

lldb/examples/python/symbolication.py

def create_target(self, debugger):
                 print('error: unable to create a valid target for (%s) "%s"' % (self.arch, self.path))
         else:
             print('error: unable to locate main executable (%s) "%s"' % (self.arch, self.path))
         return None
 
 
 class Symbolicator:
 
-    def __init__(self, debugger):
-        """A class the represents the information needed to symbolicate addresses in a program"""
+    def __init__(self, debugger=None, target=None, images=list()):
+        """A class the represents the information needed to symbolicate
+        addresses in a program.
+
+        Do not call this initializer directly, but rather use the factory
+        methods.
+        """
         self.debugger = debugger
-        self.target = None
-        self.images = list()  # a list of images to be used when symbolicating
+        self.target = target
+        self.images = images  # a list of images to be used when symbolicating
         self.addr_mask = 0xffffffffffffffff
 
     @classmethod
     def InitWithSBTarget(cls, target):
-        obj = cls()
-        obj.target = target
-        obj.images = list()
+        """Initialize a new Symbolicator with an existing SBTarget."""
+        obj = cls(target=target)
         triple = target.triple
         if triple:
             arch = triple.split('-')[0]
             if "arm" in arch:
                 obj.addr_mask = 0xfffffffffffffffe
 
         for module in target.modules:
             image = Image.InitWithSBTargetAndSBModule(target, module)
             obj.images.append(image)
         return obj
 
+    @classmethod
+    def InitWithSBDebugger(cls, debugger, images):
+        """Initialize a new Symbolicator with an existing debugger and list of
+        images. The Symbolicator will create the target."""
+        obj = cls(debugger=debugger, images=images)
+        return obj
+
     def __str__(self):
         s = "Symbolicator:\n"
         if self.target:
             s += "Target = '%s'\n" % (self.target)
             s += "Target modules:\n"
             for m in self.target.modules:
                 s += str(m) + "\n"
         s += "Images:\n"