minor symfony#20818 [Yaml] Small optimization of the parser (GuilhemN)

This PR was merged into the 3.3-dev branch.

Discussion
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[Yaml] Small optimization of the parser

| Q             | A
| ------------- | ---
| Branch?       | "master"
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets |
| License       | MIT
| Doc PR        |

Very small optimization in the Yaml parser but as it is executed often, there are performance gains (I used [this benchmark](https://gist.github.com/GuilhemN/364c4ddcc8349eaa080054d5f8ef8685); you can see the [comparison master / this PR](https://blackfire.io/profiles/compare/0f4e5497-d410-4c76-83e9-d8fa8e46ce18/graph)).

Commits
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5fc8e86 [Yaml] Small optimization of the parser

Author: fabpot

src/Symfony/Component/Yaml/Parser.php

@@ -400,7 +400,7 @@ private function getNextEmbedBlock($indentation = null, $inSequence = false)
         $blockScalarIndentations = array();
 
         if ($this->isBlockScalarHeader()) {
-            $blockScalarIndentations[] = $this->getCurrentLineIndentation();
+            $blockScalarIndentations[] = $oldLineIndentation;
         }
 
         if (!$this->moveToNextLine()) {
@@ -450,14 +450,14 @@ private function getNextEmbedBlock($indentation = null, $inSequence = false)
             // terminate all block scalars that are more indented than the current line
             if (!empty($blockScalarIndentations) && $indent < $previousLineIndentation && trim($this->currentLine) !== '') {
                 foreach ($blockScalarIndentations as $key => $blockScalarIndentation) {
-                    if ($blockScalarIndentation >= $this->getCurrentLineIndentation()) {
+                    if ($blockScalarIndentation >= $indent) {
                         unset($blockScalarIndentations[$key]);
                     }
                 }
             }
 
             if (empty($blockScalarIndentations) && !$this->isCurrentLineComment() && $this->isBlockScalarHeader()) {
-                $blockScalarIndentations[] = $this->getCurrentLineIndentation();
+                $blockScalarIndentations[] = $indent;
             }
 
             $previousLineIndentation = $indent;