Preserve target block formatting when pasting inline text

If you have a document like this:

<div style="font-size:20px">XXXX</div>
<div style="font-size:14px">YYYY</div>

and you select the YYYY text and copy it, we just copy the text to the clipboard
and not the block formatting. This is fine.

Now you select XXXX and paste. Because that removes all content from the first
block we were replacing it with the block formatting from the clipboard. But
this has no block formatting, so you essentially just "lost" the font-size:20px,
which broke user expectations.

(If the copied text *did* have block formatting, then replacing the block is
the correct thing to do in this case, which we still do.)

build/squire-raw.js

@@ -919,6 +919,7 @@ var deleteContentsOfRange = function ( range, root ) {
 // Contents of range will be deleted.
 // After method, range will be around inserted content
 var insertTreeFragmentIntoRange = function ( range, frag, root ) {
+    var firstInFragIsInline = frag.firstChild && isInline( frag.firstChild );
     var node, block, blockContentsAfterSplit, stopPoint, container, offset;
     var replaceBlock, firstBlockInFrag, nodeAfterSplit, nodeBeforeSplit;
     var tempRange;
@@ -944,11 +945,17 @@ var insertTreeFragmentIntoRange = function ( range, frag, root ) {
 
     // Merge the contents of the first block in the frag with the focused block.
     // If there are contents in the block after the focus point, collect this
-    // up to insert in the last block later. If the block is empty, replace
+    // up to insert in the last block later. This preserves the style that was
-    // it instead of merging.
+    // present in this bit of the page.
+    //
+    // If the block being inserted into is empty though, replace it instead of
+    // merging if the fragment had block contents.
+    // e.g. <blockquote><p>Foo</p></blockquote>
+    // This seems a reasonable approximation of user intent.
+
     block = getStartBlockOfRange( range, root );
     firstBlockInFrag = getNextBlock( frag, frag );
-    replaceBlock = !!block && isEmptyBlock( block );
+    replaceBlock = !firstInFragIsInline && !!block && isEmptyBlock( block );
     if ( block && firstBlockInFrag && !replaceBlock &&
             // Don't merge table cells or PRE elements into block
             !getNearest( firstBlockInFrag, frag, 'PRE' ) &&

source/Range.js

@@ -189,6 +189,7 @@ var deleteContentsOfRange = function ( range, root ) {
 // Contents of range will be deleted.
 // After method, range will be around inserted content
 var insertTreeFragmentIntoRange = function ( range, frag, root ) {
+    var firstInFragIsInline = frag.firstChild && isInline( frag.firstChild );
     var node, block, blockContentsAfterSplit, stopPoint, container, offset;
     var replaceBlock, firstBlockInFrag, nodeAfterSplit, nodeBeforeSplit;
     var tempRange;
@@ -214,11 +215,17 @@ var insertTreeFragmentIntoRange = function ( range, frag, root ) {
 
     // Merge the contents of the first block in the frag with the focused block.
     // If there are contents in the block after the focus point, collect this
-    // up to insert in the last block later. If the block is empty, replace
+    // up to insert in the last block later. This preserves the style that was
-    // it instead of merging.
+    // present in this bit of the page.
+    //
+    // If the block being inserted into is empty though, replace it instead of
+    // merging if the fragment had block contents.
+    // e.g. <blockquote><p>Foo</p></blockquote>
+    // This seems a reasonable approximation of user intent.
+
     block = getStartBlockOfRange( range, root );
     firstBlockInFrag = getNextBlock( frag, frag );
-    replaceBlock = !!block && isEmptyBlock( block );
+    replaceBlock = !firstInFragIsInline && !!block && isEmptyBlock( block );
     if ( block && firstBlockInFrag && !replaceBlock &&
             // Don't merge table cells or PRE elements into block
             !getNearest( firstBlockInFrag, frag, 'PRE' ) &&