WTF/std normalization: replace WTF::Vector::last with ::back

third_party/WebKit/Source/platform/testing/TestPaintArtifact.cpp

Index: third_party/WebKit/Source/platform/testing/TestPaintArtifact.cpp
diff --git a/third_party/WebKit/Source/platform/testing/TestPaintArtifact.cpp b/third_party/WebKit/Source/platform/testing/TestPaintArtifact.cpp
index 579525936b15fd53eb2b77577aeeee9c861f6af2..5a26c8ca832b6b2b06483a8b0a6496391caca6b7 100644
--- a/third_party/WebKit/Source/platform/testing/TestPaintArtifact.cpp
+++ b/third_party/WebKit/Source/platform/testing/TestPaintArtifact.cpp
@@ -63,7 +63,7 @@ TestPaintArtifact& TestPaintArtifact::chunk(
 TestPaintArtifact& TestPaintArtifact::chunk(
     const PaintChunkProperties& properties) {
   if (!m_paintChunks.isEmpty())
-    m_paintChunks.last().endIndex = m_displayItemList.size();
+    m_paintChunks.back().endIndex = m_displayItemList.size();
   PaintChunk chunk;
   chunk.beginIndex = m_displayItemList.size();
   chunk.properties = properties;
@@ -100,7 +100,7 @@ const PaintArtifact& TestPaintArtifact::build() {
     return m_paintArtifact;
 
   if (!m_paintChunks.isEmpty())
-    m_paintChunks.last().endIndex = m_displayItemList.size();
+    m_paintChunks.back().endIndex = m_displayItemList.size();
   m_paintArtifact = PaintArtifact(std::move(m_displayItemList),
                                   std::move(m_paintChunks), true);
   m_built = true;