Avoid nuking everything when injecting stylesheet.

third_party/WebKit/Source/core/dom/StyleEngineTest.cpp

Index: third_party/WebKit/Source/core/dom/StyleEngineTest.cpp
diff --git a/third_party/WebKit/Source/core/dom/StyleEngineTest.cpp b/third_party/WebKit/Source/core/dom/StyleEngineTest.cpp
index 59348fd59c0160ffdbb484604c97221173f0f0e0..1708917c5ee5b559f11bb81804c2a8de6e405f72 100644
--- a/third_party/WebKit/Source/core/dom/StyleEngineTest.cpp
+++ b/third_party/WebKit/Source/core/dom/StyleEngineTest.cpp
@@ -6,7 +6,9 @@
 
 #include "core/css/StyleSheetContents.h"
 #include "core/dom/Document.h"
+#include "core/dom/NodeComputedStyle.h"
 #include "core/frame/FrameView.h"
+#include "core/html/HTMLElement.h"
 #include "core/testing/DummyPageHolder.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
@@ -40,4 +42,28 @@ TEST_F(StyleEngineTest, DocumentDirtyAfterInject)
     EXPECT_TRUE(isDocumentStyleSheetCollectionClean());
 }
 
+TEST_F(StyleEngineTest, AnalyzedInject)
+{
+    document().body()->setInnerHTML("<style>div { color: red }</style><div id='t1'>Green</div><div></div>", ASSERT_NO_EXCEPTION);
+    document().view()->updateAllLifecyclePhases();
+
+    Element* t1 = document().getElementById("t1");
+    ASSERT_TRUE(t1);
+    ASSERT_TRUE(t1->computedStyle());
+    EXPECT_EQ(makeRGB(255, 0, 0), t1->computedStyle()->visitedDependentColor(CSSPropertyColor));
+
+    unsigned beforeCount = styleEngine().styleForElementCount();
+
+    RefPtrWillBeRawPtr<StyleSheetContents> parsedSheet = StyleSheetContents::create(CSSParserContext(document(), nullptr));
+    parsedSheet->parseString("#t1 { color: green }");
+    styleEngine().injectAuthorSheet(parsedSheet);
+    document().view()->updateAllLifecyclePhases();
+
+    unsigned afterCount = styleEngine().styleForElementCount();
+    EXPECT_EQ(1u, afterCount - beforeCount);
+
+    ASSERT_TRUE(t1->computedStyle());
+    EXPECT_EQ(makeRGB(0, 128, 0), t1->computedStyle()->visitedDependentColor(CSSPropertyColor));
+}
+
 } // namespace blink