DevTools: introduce spritesheet assembler.

third_party/WebKit/Source/devtools/scripts/assemble_spritesheet.js

+#!/usr/bin/env node
+
+var path = require('path');
+var exec = require('child_process').exec;
+var writeSVGAndDescriptors = require('./spritesheet_assembler');
+
+// Write new spritesheet.
+var frontendFolder = path.join(__dirname, '..', 'front_end');
+var iconsFolder = path.join(frontendFolder, 'Images', 'icons');
+var outputSVGPath = path.join(frontendFolder, 'Images', 'src', 'icons_spritesheet.svg');
+var outputJSPath = path.join(frontendFolder, 'ui', 'GeneratedIconDescriptors.js');
+writeSVGAndDescriptors(iconsFolder, 1, outputSVGPath, outputJSPath);
+
+// Convert SVG to PNG.
+var convertScript = 'convert_svg_images_to_png.py';
+var convertScriptPath = path.join(__dirname, convertScript);
+var cmd = 'python ' + convertScriptPath;
+console.log('Running ' + convertScript);
+exec(cmd, function(error, stdout, stderr) {
+  if (error) {
+    console.error(stderr);
+    return;
+  }
+  console.log(stdout);
+  console.log('DONE. Don\'t forget to optimize your images!');
+});