deps: cherry-pick 2987946 from upstream V8

Original commit message:

    Stop manual unescaping of script source data when preprocessing logs.

    It appears that the fields are already being unescaped elsewhere,
    perhaps by the JSON writer. So if we unescape when adding the source
    filename and contents, unescaping will happen again later and plain
    backslashes will be interpreted as escape codes.

    Bug: v8:6240
    Change-Id: Ic66b9017ae685d6dd12944ee8d254991e26fbd32
    Reviewed-on: https://chromium-review.googlesource.com/1186625
    Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
    Commit-Queue: Bret Sepulveda <bsep@chromium.org>
    Cr-Commit-Position: refs/heads/master@{#55401}

Refs: v8/v8@2987946

common.gypi

@@ -33,7 +33,7 @@
 
     # Reset this number to 0 on major V8 upgrades.
     # Increment by one for each non-official patch applied to deps/v8.
-    'v8_embedder_string': '-node.44',
+    'v8_embedder_string': '-node.45',
 
     # Enable disassembler for `--print-code` v8 options
     'v8_enable_disassembler': 1,

deps/v8/tools/profile.js

@@ -1002,33 +1002,10 @@ JsonProfile.prototype.addSourcePositions = function(
   };
 };
 
-function unescapeString(s) {
-  s = s.split("\\");
-  for (var i = 1; i < s.length; i++) {
-    if (s[i] === "") {
-      // Double backslash.
-      s[i] = "\\";
-    } else if (i > 0 && s[i].startsWith("x")) {
-      // Escaped Ascii character.
-      s[i] = String.fromCharCode(parseInt(s[i].substring(1, 3), 16)) +
-          s[i].substring(3);
-    } else if (i > 0 && s[i].startsWith("u")) {
-      // Escaped unicode character.
-      s[i] = String.fromCharCode(parseInt(s[i].substring(1, 5), 16)) +
-          s[i].substring(5);
-    } else {
-      if (i > 0 && s[i - 1] !== "\\") {
-        printErr("Malformed source string");
-      }
-    }
-  }
-  return s.join("");
-}
-
 JsonProfile.prototype.addScriptSource = function(script, url, source) {
   this.scripts_[script] = {
-    name : unescapeString(url),
-    source : unescapeString(source)
+    name : url,
+    source : source
   };
 };