setChildrenInline wasn't doing anything and childrenInlien always deferred to isRenderParagraph.

Also, add a test from the original webkit patch that called setChildrenInline in layoutBlock

R=ojan@chromium.org

Review URL: https://codereview.chromium.org/748943002

engine/src/flutter/tests/editing/delete_block_contents-expected.txt

@@ -0,0 +1,5 @@
+Running 1 tests
+ok 1 height of an editable block remains the same after adding block elements and removing them
+1 tests
+1 pass
+0 fail

engine/src/flutter/tests/editing/delete_block_contents.sky

@@ -0,0 +1,28 @@
+<sky>
+<import src="../resources/chai.sky" />
+<import src="../resources/mocha.sky" />
+This test verifies that the height of an editable block remains the same after adding block elements and removing them.
+<div contenteditable="true" style="border: solid blue" id="test"></div>
+<script>
+describe("height of an editable block", function(done) {
+  it("remains the same after adding block elements and removing them", function() {
+    var elem = document.getElementById("test");
+    var originalHeight = elem.offsetHeight;
+    var d = elem.appendChild(document.createElement('div'));
+    d.appendChild(document.createTextNode('aaa'));
+    d = elem.appendChild(document.createElement('div'));
+    d.appendChild(document.createTextNode('bbb'));
+    var newHeight = elem.offsetHeight;
+
+    while (elem.firstChild) {
+       elem.removeChild(elem.firstChild);
+    }
+
+    setTimeout(function() {
+      assert.equal(elem.offsetHeight, originalHeight);
+      done();
+    });
+  });
+})
+</script>
+</sky>