Remove initial whitespace & empty lines to decrease JS files size

Patch will decrease size of JS files included into Chrome APK
(about 11 KB now)

Bug: 
Change-Id: I701c9904fbf22fd295199f255601dea6524a3766
Reviewed-on: https://chromium-review.googlesource.com/821071Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Marcin Wiącek <marcin@mwiacek.com>
Cr-Commit-Position: refs/heads/master@{#50179}

AUTHORS

@@ -96,6 +96,7 @@ Luis Reis <luis.m.reis@gmail.com>
 Luke Zarko <lukezarko@gmail.com>
 Maciej Małecki <me@mmalecki.com>
 Marcin Cieślak <saper@marcincieslak.com>
+Marcin Wiącek <marcin@mwiacek.com>
 Mateusz Czeladka <mateusz.szczap@gmail.com>
 Mathias Bynens <mathias@qiwi.be>
 Matt Hanselman <mjhanselman@gmail.com>

tools/js2c.py

@@ -50,10 +50,12 @@ def ToCArray(byte_sequence):
   return textwrap.fill(joined, 80)
 
 
-def RemoveCommentsAndTrailingWhitespace(lines):
+def RemoveCommentsEmptyLinesAndWhitespace(lines):
+  lines = re.sub(r'\n+', '\n', lines) # empty lines
   lines = re.sub(r'//.*\n', '\n', lines) # end-of-line comments
   lines = re.sub(re.compile(r'/\*.*?\*/', re.DOTALL), '', lines) # comments.
-  lines = re.sub(r'\s+\n+', '\n', lines) # trailing whitespace
+  lines = re.sub(r'\s+\n', '\n', lines) # trailing whitespace
+  lines = re.sub(r'\n\s+', '\n', lines) # initial whitespace
   return lines
 
 
@@ -342,7 +344,7 @@ def BuildFilterChain(macro_filename, message_template_file):
     filter_chain.append(lambda l: ExpandConstants(l, message_templates))
 
   filter_chain.extend([
-    RemoveCommentsAndTrailingWhitespace,
+    RemoveCommentsEmptyLinesAndWhitespace,
     ExpandInlineMacros,
     ExpandInlineConstants,
     Validate,
@@ -355,7 +357,7 @@ def BuildFilterChain(macro_filename, message_template_file):
   return reduce(chain, filter_chain)
 
 def BuildExtraFilterChain():
-  return lambda x: RemoveCommentsAndTrailingWhitespace(Validate(x))
+  return lambda x: RemoveCommentsEmptyLinesAndWhitespace(Validate(x))
 
 class Sources:
   def __init__(self):