Revert "[inspector] breakpoint after last break position should not jump to first line"

This reverts commit 61292f0b.

Reason for revert: Breaks layout tests:
https://build.chromium.org/p/client.v8.fyi/builders/V8-Blink%20Linux%2064/builds/18913

Original change's description:
> [inspector] breakpoint after last break position should not jump to first line
> 
> R=​jgruber@chromium.org
> 
> Bug: chromium:730177
> Change-Id: I0f3666a333604cb80bb51410c5edf2aceb0c6ef5
> Reviewed-on: https://chromium-review.googlesource.com/717717
> Commit-Queue: Aleksey Kozyatinskiy <kozyatinskiy@chromium.org>
> Reviewed-by: Jakob Gruber <jgruber@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#48556}

TBR=kozyatinskiy@chromium.org,jgruber@chromium.org

Change-Id: Ic4e961bf9c82e43281779c79e22660a55bfcb29d
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: chromium:730177
Reviewed-on: https://chromium-review.googlesource.com/720376Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48567}

src/debug/debug.cc

@@ -603,13 +603,8 @@ bool Debug::SetBreakPointForScript(Handle<Script> script,
 
   Handle<DebugInfo> debug_info(shared->GetDebugInfo());
 
-  // Find breakable position returns first breakable position after
-  // *source_position, it can return 0 if no break location is found after
-  // *source_position.
-  int breakable_position = FindBreakablePosition(debug_info, *source_position);
-  if (breakable_position < *source_position) return false;
-  *source_position = breakable_position;
-
+  // Find the break point and change it.
+  *source_position = FindBreakablePosition(debug_info, *source_position);
   DebugInfo::SetBreakPoint(debug_info, *source_position, break_point_object);
   // At least one active break point now.
   DCHECK_LT(0, debug_info->GetBreakPointCount());

test/debugger/debug/regress/regress-crbug-517592.js

@@ -4,7 +4,7 @@
 
 var source =
   "var foo = function foo() {\n" +
-  "  var a = 1;\n" +
+  "  return 1;\n" +
   "}\n" +
   "//@ sourceURL=test";
 

test/inspector/debugger/set-breakpoint-at-last-line-expected.txt

-Tests breakpoint at last line.
-{
-    breakpointId : <breakpointId>
-    locations : [
-        [0] : {
-            columnNumber : 12
-            lineNumber : 3
-            scriptId : <scriptId>
-        }
-    ]
-}
-{
-    breakpointId : <breakpointId>
-    locations : [
-    ]
-}

test/inspector/debugger/set-breakpoint-at-last-line.js

-// Copyright 2017 the V8 project authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-let {session, contextGroup, Protocol} = InspectorTest.start('Tests breakpoint at last line.');
-
-let source = `
-  let a = 1;
-  //# sourceURL=foo.js
-  let b = 2;
-`;
-
-(async function test() {
-  Protocol.Debugger.enable();
-  Protocol.Runtime.evaluate({expression: source});
-  let {result} = await Protocol.Debugger.setBreakpointByUrl({
-    url: 'foo.js',
-    lineNumber: 3,
-    columnNumber: 12
-  });
-  InspectorTest.logMessage(result);
-  ({result} = await Protocol.Debugger.setBreakpointByUrl({
-    url: 'foo.js',
-    lineNumber: 4
-  }));
-  InspectorTest.logMessage(result);
-  InspectorTest.completeTest();
-})();