Make previousPositionOf() to handle yet another no previous position case

third_party/WebKit/Source/core/editing/VisibleUnitsTest.cpp

Index: third_party/WebKit/Source/core/editing/VisibleUnitsTest.cpp
diff --git a/third_party/WebKit/Source/core/editing/VisibleUnitsTest.cpp b/third_party/WebKit/Source/core/editing/VisibleUnitsTest.cpp
index 4c5d43212cafe3576c65dbb799e8de1137dd80e7..4ffe01bc3feab8e3600c449b10b737ce123e3d57 100644
--- a/third_party/WebKit/Source/core/editing/VisibleUnitsTest.cpp
+++ b/third_party/WebKit/Source/core/editing/VisibleUnitsTest.cpp
@@ -1048,6 +1048,18 @@ TEST_F(VisibleUnitsTest, previousPositionOfOneCharPerLine)
     EXPECT_EQ(PositionWithAffinity(Position(sample, 1)), previousPositionOf(createVisiblePosition(Position(sample, 2), TextAffinity::Upstream)).toPositionWithAffinity());
 }
 
+TEST_F(VisibleUnitsTest, previousPositionOfNoPreviousPosition)
+{
+    setBodyContent(
+        "<span contenteditable='true'>"
+            "<span> </span>"
+            " " // This whitespace causes no previous position.
+            "<div id='anchor'> bar</div>"
+        "</span>");
+    const Position position(document().getElementById("anchor")->firstChild(), 1);
+    EXPECT_EQ(Position(), previousPositionOf(createVisiblePosition(position)).deepEquivalent());
+}
+
 TEST_F(VisibleUnitsTest, rendersInDifferentPositionAfterAnchor)
 {
     const char* bodyContent = "<p id='sample'>00</p>";