MAGETWO-57656: Base url should be processed while sending email

Author: Karpenko, Oleksandr

app/code/Magento/Email/Model/Template/Filter.php

@@ -930,8 +930,8 @@ public function getCssFilesContent(array $files)
             foreach ($files as $file) {
                 $asset = $this->_assetRepo->createAsset($file, $designParams);
                 $pubDirectory = $this->getPubDirectory($asset->getContext()->getBaseDirType());
-                if ($pubDirectory->isExist($asset->getRelativeSourceFilePath())) {
-                    $css .= $pubDirectory->readFile($asset->getRelativeSourceFilePath());
+                if ($pubDirectory->isExist($asset->getPath())) {
+                    $css .= $pubDirectory->readFile($asset->getPath());
                 } else {
                     $css .= $asset->getContent();
                 }

app/code/Magento/Email/Test/Unit/Model/Template/FilterTest.php

@@ -7,7 +7,9 @@
 use Magento\Email\Model\Template\Css\Processor;
 use Magento\Email\Model\Template\Filter;
 use Magento\Framework\App\Area;
+use Magento\Framework\App\Filesystem\DirectoryList;
 use Magento\Framework\Filesystem\Directory\ReadInterface;
+use Magento\Framework\View\Asset\File\FallbackContext;
 
 /**
  * @SuppressWarnings(PHPMD.CouplingBetweenObjects)
@@ -292,21 +294,25 @@ public function testGetCssFilesContent()
             'theme' => 'themeId',
             'locale' => 'localeId',
         ];
-
         $filter = $this->getModel();
 
         $asset = $this->getMockBuilder(\Magento\Framework\View\Asset\File::class)
             ->disableOriginalConstructor()
             ->getMock();
-        $fallbackContext = $this->getMockBuilder(\Magento\Framework\View\Asset\File\FallbackContext::class)
+
+        $fallbackContext = $this->getMockBuilder(FallbackContext::class)
             ->disableOriginalConstructor()
             ->getMock();
         $fallbackContext->expects($this->once())
-            ->method('getPath')
-            ->willReturn($path);
+            ->method('getBaseDirType')
+            ->willReturn(DirectoryList::STATIC_VIEW);
         $asset->expects($this->atLeastOnce())
             ->method('getContext')
             ->willReturn($fallbackContext);
+
+        $asset->expects($this->atLeastOnce())
+            ->method('getPath')
+            ->willReturn($path . DIRECTORY_SEPARATOR . $file);
         $this->assetRepo->expects($this->once())
             ->method('createAsset')
             ->with($file, $designParams)