gn2bp: Remove unused ODRChecker

Test: ./gen_android_bp --desc gn.json --output Android.bp \
'//third_party/zlib:zlib'

Change-Id: I3f27e552e4134a22e32cf64822bab08958340bbd
diff --git a/tools/gn2bp/gn_utils.py b/tools/gn2bp/gn_utils.py
index 95f677a..6163ea0 100644
--- a/tools/gn2bp/gn_utils.py
+++ b/tools/gn2bp/gn_utils.py
@@ -207,80 +207,6 @@
   return res
 
 
-class ODRChecker(object):
-  """Detects ODR violations in linker units
-
-  When we turn GN source sets into Soong & Bazel file groups, there is the risk
-  to create ODR violations by including the same file group into different
-  linker unit (this is because other build systems don't have a concept
-  equivalent to GN's source_set). This class navigates the transitive
-  dependencies (mostly static libraries) of a target and detects if multiple
-  paths end up including the same file group. This is to avoid situations like:
-
-  traced.exe -> base(file group)
-  traced.exe -> libperfetto(static lib) -> base(file group)
-  """
-
-  def __init__(self, gn, target_name):
-    self.gn = gn
-    self.root = gn.get_target(target_name)
-    self.source_sets = collections.defaultdict(set)
-    self.deps_visited = set()
-    self.source_set_hdr_only = {}
-
-    self._visit(target_name)
-    num_violations = 0
-    if target_name in ODR_VIOLATION_IGNORE_TARGETS:
-      return
-    for sset, paths in self.source_sets.items():
-      if self.is_header_only(sset):
-        continue
-      if len(paths) != 1:
-        num_violations += 1
-        print(
-            'ODR violation in target %s, multiple paths include %s:\n  %s' %
-            (target_name, sset, '\n  '.join(paths)),
-            file=sys.stderr)
-    if num_violations > 0:
-      raise Exception('%d ODR violations detected. Build generation aborted' %
-                      num_violations)
-
-  def _visit(self, target_name, parent_path=''):
-    target = self.gn.get_target(target_name)
-    path = ((parent_path + ' > ') if parent_path else '') + target_name
-    if not target:
-      raise Exception('Cannot find target %s' % target_name)
-    for ssdep in target.source_set_deps:
-      name_and_path = '%s (via %s)' % (target_name, path)
-      self.source_sets[ssdep].add(name_and_path)
-    deps = set(target.deps).union(
-        target.transitive_proto_deps) - self.deps_visited
-    for dep_name in deps:
-      dep = self.gn.get_target(dep_name)
-      if dep.type == 'executable':
-        continue  # Execs are strong boundaries and don't cause ODR violations.
-      # static_library dependencies should reset the path. It doesn't matter if
-      # we get to a source file via:
-      # source_set1 > static_lib > source.cc OR
-      # source_set1 > source_set2 > static_lib > source.cc
-      # This is NOT an ODR violation because source.cc is linked from the same
-      # static library
-      next_parent_path = path if dep.type != 'static_library' else ''
-      self.deps_visited.add(dep_name)
-      self._visit(dep_name, next_parent_path)
-
-  def is_header_only(self, source_set_name):
-    cached = self.source_set_hdr_only.get(source_set_name)
-    if cached is not None:
-      return cached
-    target = self.gn.get_target(source_set_name)
-    if target.type != 'source_set':
-      raise TypeError('%s is not a source_set' % source_set_name)
-    res = all(src.endswith('.h') for src in target.sources)
-    self.source_set_hdr_only[source_set_name] = res
-    return res
-
-
 class GnParser(object):
   """A parser with some cleverness for GN json desc files