Remove references to GClientKeywords.FromImpl from roll scripts

This class was removed because it was no longer used but some roll
scripts were still referencing it. Also removes a dummy FromImpl in
PRESUBMIT.py as it shouldn't be needed anymore.

TBR=dpranke@chromium.org

BUG=661382

Review-Url: https://codereview.chromium.org/2898403003
Cr-Commit-Position: refs/heads/master@{#474329}

PRESUBMIT.py

@@ -1140,12 +1140,6 @@ def _ExtractAddRulesFromParsedDeps(parsed_deps):
 def _ParseDeps(contents):
   """Simple helper for parsing DEPS files."""
   # Stubs for handling special syntax in the root DEPS file.
-  def FromImpl(*_):
-    pass  # NOP function so "From" doesn't fail.
-
-  def FileImpl(_):
-    pass  # NOP function so "File" doesn't fail.
-
   class _VarImpl:
 
     def __init__(self, local_scope):
@@ -1160,8 +1154,6 @@ def Lookup(self, var_name):
 
   local_scope = {}
   global_scope = {
-      'File': FileImpl,
-      'From': FromImpl,
       'Var': _VarImpl(local_scope).Lookup,
   }
   exec contents in global_scope, local_scope

tools/roll_angle.py

@@ -81,7 +81,6 @@ def _ParseDepsDict(deps_content):
   local_scope = {}
   var = GClientKeywords.VarImpl({}, local_scope)
   global_scope = {
-    'From': GClientKeywords.FromImpl,
     'Var': var.Lookup,
     'deps_os': {},
   }

tools/roll_swiftshader.py

@@ -87,7 +87,6 @@ def _ParseDepsDict(deps_content):
   local_scope = {}
   var = GClientKeywords.VarImpl({}, local_scope)
   global_scope = {
-    'From': GClientKeywords.FromImpl,
     'Var': var.Lookup,
     'deps_os': {},
   }

tools/roll_webgl_conformance.py

@@ -83,7 +83,6 @@ def _ParseDepsDict(deps_content):
   local_scope = {}
   var = GClientKeywords.VarImpl({}, local_scope)
   global_scope = {
-    'From': GClientKeywords.FromImpl,
     'Var': var.Lookup,
     'deps_os': {},
   }

tools/roll_webrtc.py

@@ -96,7 +96,6 @@ def _ParseDepsDict(deps_content):
   local_scope = {}
   var = GClientKeywords.VarImpl({}, local_scope)
   global_scope = {
-#    'From': GClientKeywords.FromImpl,
     'Var': var.Lookup,
     'deps_os': {},
   }